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1. ve Ne Did you perform the On Board OBD System Check Go to m 2 Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent section Repair wire Refer to harness shorted Diagnostic Aids signal to for DTC 224 voltage Refer to Wiring Repairs in Engine Electrical IMPCO Technologies Engine Service Manual 103 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 241 Adaptive Lean Fault high limit gasoline DK GRN ORN Sensor Ground PNK DK GRN To System Power Relay To Engine Ground Conditions for Setting the DTC Heated Oxygen Sensor Functional Fault Adaptive multiplier out of range greater than 30 MIL On during active adaptive limit condition Adaptive Enabled Closed Loop Enabled Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the Adaptive multiplier This fault sets if the Adaptive multiplier exceeds the limits of normal operation Diagnostic Aids If any other DTCs are present diagnose those first Oxygen Sensor Wire Heated Oxygen sensor wires may be mis routed and contacting the exhaust manifold Vacuum Leaks Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at especially at light load
2. Gauges Malfunction Indicator Lamp Figure 10 LPG Engine control module ECM The controller also performs diagnostic functions on the fuel system and notifies the operator of engine malfunctions by A C AU TI O N turning on a Malfunction Indicator Light MIL mounted in the dash Malfunctions in the system are identified by a Diagnostic Trouble Code number In addition to notifying the The Heated Exhaust Gas Oxygen operator of the malfunetion in the system the controller also Sensor HEGO is an emissions stores the information about the malfunction in its memory control component If the HEGO fails A technician can than utilize a computerized diagnostic scan to operate replace only with an OEM tool to retrieve the stored diagnostic code and by using the replacement part The HEGO sensor diagnostic charts in this manual determine the cause of the BE mi is sensitive to silicone and silicone malfunction In the event a technician does not have the computerized diagnostic tool the MIL light can be used to based products and can become identify the diagnostic code By following specific steps contaminated Avoid using silicone the technician can activate the blink feature and count the sealers or hoses treated with silicone number of blinks to determine the diagnostic code number to lubricant in the air stream or fuel sup locate the fault in the system ply lines HEATED EXHAUST GAS OXYGEN SENSOR The
3. Important Do not use the old cap CMP sensor and ro tor screws Use the replacement screws that have been coated with a thread locking compound 1 Insert the CMP sensor through the reluctor wheel slot 301398 2 Install new CMP mounting screws Tighten Tighten the bolts to 2 2 N m 19 Ib in 4341 3 Install the rotor onto the reluctor wheel 156748 32 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 4 Install new rotor screws Tighten Tighten the screws to 2 N m 18 Ib in 4354 5 Install the distributor cap 157986 6 Install new distributor cap screws Tighten Tighten the screws to 2 4 N m 21 Ib in 157984 IMPCO Technologies Engine Service Manual 33 302829 8 Connect the spark plug wires and ignition coil wire Refer to Spark Plug Wire Replacement 302854 34 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Fuel System 1E1 SECTION 1E1 FUEL SYSTEM IMPCO Technologies Engine Service Manual 1 1E1 Fuel System REPAIR INSTRUCTIONS PROPANE FUEL SYSTEM PRESSURE RELIEF THE PROPANE FUEL SYSTEM OPERATES AT PRESSURES UP TO 21 5 BAR 312 PSI TO MINIMIZE THE RISK OF FIRE AND PERSONAL INJURY RELIEVE THE PRO PANE FUEL SYSTEM PRESSURE WHERE APPLICABLE BEFORE SERVICING THE PROPANE FUEL SYSTEM COMPONENTS To relieve propane fuel system pressure 1 Close t
4. 5 Unscrew the LPL from the LPR inlet fitting 9o m PRESSURE TRIM VALVE PTV Installation Procedure REPLACEMENT IMPORTANT Figure 2 e Do not use Teflon tape on any fuel fitting Use a Disconnect the PTV electrical connection liquid pipe thread sealant when installing fittings Removethe vacuum hase fromthe PTV Remove and retain the two 2 retaining bolts and plate Remove the PTV Bon 1 Apply pipe thread sealant to the LPR inlet fitting 2 Install the LPL to the LPR Tighten the LPL finger tight plus 1 to 2 turns and place the LPL in the correct posi IMPCO Technologies Engine Service Manual 3 1E1 Fuel System Installation Procedure IMPORTANT a small amount of O ring lubricant to the PTV O ring before installation Install the PTV using the two mounting bolts and re taining plate Tighten retaining bolts Tighten 9 Nem 80 Ib in Connect the PTV vacuum line Connect the PTV electrical connector Start the vehicle Connect the diagnostic service tool and verify the engine is operating in closed loop and no MIL light is present LOW PRESSURE REGULATOR LPR REPLACEMENT Figure 2 Removal Procedure 1 4 Relieve the propane fuel system pressure Refer to Propane Fuel System Pressure Relief Disconnect the negative battery cable Clamp the coolant hoses to the LPR or drain the radia tor Remove the LPL Refer to Low Pressure Lock off Replacement Remove the PTV
5. DTC 222 Closed Loop Multiplier Low en Did you perform the OBD System Check mam to e 2 Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine to full operating temperature and then idle for a minimum of 2 minutes Does DST display HO2S voltage fixed above 0 7 volts after 2 minutes of idle run time Disconnect 25 wire harness connector Disconnect ECM wiring harness connector Wiring Repairs Using a high impedance DVOM check for voltage between HO2S connector signal pin and engine Do you have voltage Go to OBD System Check Section Intermittent problem Go to Intermittent section Refer to Diagnostic Aids for DTC 222 IMPCO Technologies Engine Service Manual 101 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 224 Closed Loop Multiplier Low LPG lt gt Sensor Ground Heater To Engine Ground System Power Relay Conditions for Setting the DTC Heated Oxygen Sensor Functional Fault Closed Loop multiplier out of range at limit of 35 MIL Disabled Adaptive Disabled Closed Loop Enabled Circuit Description The HO2S Heated Oxygen Sensor sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen
6. Frozen bearings 4 Failure to operate with no current draw indi cates Open brush circuit This can be checked after disassembly by inspecting internal connections and tracing circuit with a test lamp Open armature coils Inspect commuta tor for badly burned bars after disassembly Broken brush springs worn brushes high insulation between the commutator bars or other causes which would prevent good contact between the brushes and commuta tor 5 Low no load speed and low current draw indicates High internal resistance due to poor connec tions defective leads dirty commutator and causes listed under number 4 6 High free speed and high current draw may Starter 1C5 indicate shorted armature Check for shorted armature using a growler STARTER MOTOR DISASSEMBLY Figure 4 16 Refer to Specifications in this section for appli cation Remove or Disconnect 1 Lead from solenoid terminal 2 Solenoid retaining bolts 3 Through bolts 4 Screws and commutator end frame from motor assembly brush assembly and bearing remain on armature Magnets in frame have strong attraction to metal parts Keep fingers clear of pinch points to avoid personal injury CAUTION 5 Armature from field frame 6 Frame and shield from drive end housing assembly 7 Use J 28509 A or eguivalent to pull bearing from armature The bearing is press fit over shaft NOTICE Before r
7. IMPCO Technologies Engine Service Manual 83 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 144 Camshaft Sensor Loss Dist Cam 5 volts Conditions for Setting the DTC CMP Camshaft Position Sensor Check Condition Engine Cranking or Running Fault Condition No cam pulse in 3 cycles MIL On for active fault and for 10 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The CMP Camshaft Position Sensor is used to synchronize the fuel and ignition systems This fault will set ifthe ECM does not detect a cam pulse in 3 engine cycles whenever the engine is cranking or running The engine will not run with this fault present 84 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 144 Camshaft Sensor Loss Ye No Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to Step 3 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical e Key On Engine OFF 5 0 volts Go to Step 4 Repair the circuit e Disconnect the CMP Camshaft position Sensor as necessary connector C011 Refer to Wiring e Using A DVOM check for voltage at the CMP Repairs in Engine sensor connector pin C and engine ground Electrical Do you have voltage Key OFF Go to Step 5 Rep
8. This fault will set if the signal voltage is less than 0 05 volts anytime the engine is cranking or running The ECM will use the default value for the IAT sensor in the event of this fault 22 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 112 IAT VOLTAGE LOW BOSCH TMAP DST Diagnostic Scan Tool connected in System Data Mode Disconnect the TMAP sensor wire harness connector Key ON Does Disconnect ECM wire harness connector Check for continuity between TMAP sensor connector ground pin 1 and TMAP sensor connector signal pin 2 Do you have continuity between them connector signal circuit pin 2 and engine ground Do you have continuity Replace Refer to M replacement in the Engine Controls Section Is the replacement complete e Remove all test equipment except the D Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 112 check for any stored codes Does the engine operate normally with no stored codes oto System Check Section o to step problem Go to Intermittent section NE the o to step 6 circuit as necessary Re
9. COIL CONNECTOR C007 Pink Dk Green B Yellow Black __ IMPCO Technologies Engine Service Manua 19 1C2 Wiring Sci ti 1 3 liter Emission Certified GM Enai MODULE CONNECTOR C008 Pink Dk Green B Yellow D j Yelow Black 20 IMPCO Technologies Engine Service Manual SENSOR CONNECTOR C009 Lt Green Red 5 Volt Reference B White Purple IMPCO Technologies Engine Service Manual 21 EGO SENSOR CONNECTOR C010 BIK Lt Green Pink Dk Green Pin ___ EGO D 22 IMPCO Technologies Engine Service Manual CAM CONNECTOR C011 Purple Orange B Grey Brown Lt Green Red 5 Volt Ref IMPCO Technologies Engine Service Manual 23 1C2 Wiring Sci ti 1 3 liter Emission Certified GM Engi THROTTLE CONNECTOR C012 1 Tan Orange 2 PinkMhite 24 IMPCO Technologies Engine Service Manual 013 Bosch TMAP used with gasoline Motorola TMAP used with LPG fuel system only fuel system only 1 A Black Lt Green Analog Return AT Lt Green Red Volt Reference IMPCO Technologies Engine Service Manual 25 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi STARTER SOLENOID CONNECTOR C014 Pin Wire Color Function 26 IMPCO Technologies Engine Service Manual ECT CONNECTOR C015 Pin Wire Color Yellow Gray __ Bl
10. Go to Step 8 Go to Step 7 Key ON Engine OFF DST in Active Fault Mode Are any other DTC codes present with DTC 651 Diagnose any other DTC codes before proceeding with this chart Have any other DTC codes been diagnosed and repaired Check the Service Part Number on the ECM to ensure correct calibration is in use Is the Service Part Number Correct Replace ECM with correct Service Part Number Is the replacement complete Check the mechanical operation of the throttle Is the mechanical operation of the throttle OK Check engine for large manifold vacuum leaks Refer to Fuel Systems Section 1B Symptom Diagnostics Did you find and correct the vacuum leak Go to Step 9 Go to OBD System Check Section System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 169 Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 653 check for any stored codes Does the engine operate normally with no stored codes Correct mechanical operation of the throttle Refer Go to step 9 to Engine amp Component R amp R Section Has the mechanical operation of the throttle been correc
11. IMPCO Technologies Engine Service Manual 115 Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 244 check for any stored codes Does the engine operate normally with no stored codes Key OFF Repair the Go to Step 5 Disconnect HO2S sensor wire harness connector circuit as Disconnect ECM wire harness connector Refer to Key ON Wiring Repairs Using a DVOM check for voltage at HO2S in Engine connector signal pin B and engine ground Electrical 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 261 System Voltage Low ECM a 19 GROUND 20 RIT 22 VBAT RI 23 Conditions for Setting the DTC System Voltage to ECM Check Condition Key on and RPM greater than 1500 Fault Condition Battery voltage at ECM less than 9 0 volts continuously for 5 seconds MIL On for active fault and for 10 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The battery voltage powers the ECM and must be measured to correctly operate injector drivers fu
12. kode GASOLINE ONLY saareen L seat Om MT Se PN SH DO mt m PI o os 1 cea ses es SONG EO SENG DE uns ei u rm 4 ACK BAKTE prem RED TAN 16 G1 El ROUND F1 PINKTAN 18 c011 DIST CAM co22 BLACKATGREEN 18 SN ee SS T m NH E an E ang L H TANJBROWN 18 SH CRAYOK LUE TE Tanin Za SVE MATE TS s sa PURPLE DKBLUETE AUXOUTI co16 co14 STARTER_RELAY 87A _LTBLUE PINK16 co24 OH BLACK WHITE 18 STARTER PiNKTAN1s Hy SOLENOID ur i GRAV ORANGE 18 85 d An F RELAY FUSED POWER co18 FUEL_PUMP_RELAY o EL PINKYELLOW 16 PINK YELLOW 16 F3 RED 14 PINK TAN 18 TAN BLACK 18 20 IH ALTERNATOR CO17 POWER RELAY C021 RED 14 30 9 mm ne 2 ALTERNATOR F4 WHITE BLUE18 gs 12162193 IMPCO Technologies Engine Service Manual 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi 4 3L LPG JUMP HARNESS CO27 FUEL TRIM WHITE RED 18 A ORANGE BLUE 16 B CO26 LOCKOFF WHITE BLACK 18 PINK TAN 18 8 IMPCO Technologies Engine Service Manual 27 PRESSURE TRIM ORANGE BLUE 16 RED WHITE 18 WHITE BLACK 18 WHITE RED 18 PINK TAN 18 CO04 E NUMOO
13. 54 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 55 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 132 MAP Low Voltage Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Manifold Absolute Pressure Check Condition Cranking or Running Fault Condition MAP voltage less than 0 05 Throttle Position greater than 2 and engine RPM less than 7000 MIL On for remainder of key on cycle Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Misc Fueling is based on RPM and TPS Limp Home Condition during this fault Circuit Description The Manifold Absolute Pressure sensor is a pressure transducer connected to the intake manifold It is used to measure the pressure of air in the manifold prior to induction into the engine The pressure reading is used in conjunction with other inputs to determine the airflow rate to the engine which determines the fuel flow rate This fault will set when the MAP reading is lower than the sensor should normally produce When this fault is set the Adaptive Learn will be disabled for the remainder of the key on cycle and the MIL will be on 56 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 132 MAP Low Voltage Bosche TMAP e Key On Engine running problem e DSC Diagnostic Scan Tool connected in Go to System Data Mode Intermittent
14. Inspect exhaust system for restrictions Refer to Go to Symptoms Restricted Exhaust in Engine Exhaust Engine Did you find and correct the condition Go to Step 17 Mechanical IMPCO Technologies Engine Service Manual 19 1C7 Ignition System 4 3 liter Emission Certified GM Engine DTC P0300 cont d Sep Action Vas Ye No 1 Use the scan tool in order to clear the DTCs 2 Turn the ignition OFF for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC Does the DTC run and pass Go to Step 18 Go to Step 2 With a scan tool observe the stored information Go to Diagnostic Trouble Code DTC List System OK Capture Info Does the scan tool display any DTCs that you have not diagnosed 20 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0325 SIE ID 693514 Circuit Description stores this information in the Failure Records If The knock sensor KS produces an AC voltage at all the diagnostic reports a failure on the engine speeds and loads The powertrain control second consecutive ignition cycle the control module PCM then adjusts the spark timing based on module records the operating conditions at the amplitude and frequency of the KS signal The the time of the failure The control module writes PCM uses the KS signal to calculate the average the operating conditions to the Freeze Fra
15. Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Engine Mechanical Check Important The LPG Fuel system works on a fumigation principle of fuel introduction and is more sensitive to intake manifold leakage than a gasoline fuel supply system e Check the engine for the following Improper valve timing Engine compression Manifold vacuum leaks Intake manifold gaskets Sticking or leaking valves Exhaust system leakage e Check the intake and exhaust system for casting flash or other restrictions Fuel System Checks e Perform a fuel system diagnosis Refer to LPG Fuel System Diagnosis 10 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Lack of Power Sluggishness or Sponginess DEFINITION The engine delivers less than expected power There is little or no increase in speed when partially applying the accelerator pedal Preliminary Checks Fuel System Checks Sensor Checks Exhaust System Checks Engine Mechanical Check Additional Check Refer to Important Preliminary Checks Refer to the LPG Fuel system OBD System Check Compare the customer s vehicle with a similar unit Make sure the customer has an actual problem Do not compare the power output of the vehicle operating on LPG to a vehicle operating on gasoline as the fuels do have different drive feel characteris
16. Value s ves Ne 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code section Does DTC 515 reset with the engine idling 3 e Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical e Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 515 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 129 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 516 Ram Failure Microprocessor Conditions for Setting the DTC Random Access Memory Check Condition Key On Fault Condition Internal ECM memory access failure MIL On un
17. Verify proper fuel pump pressure Verify proper Fuel rail pressure Refer to the Gasoline Fuel System Diagnosis Check Electrical connections at the injectors Check for the proper ignition voltage output with J 26792 or the equivalent that spark plugs are correct use R42LTS Check for faulty spark plug wires Check for fouled spark plugs Check for manifold vacuum or air induction system leaks Check the generator output voltage IMPCO Technologies Engine Service Manual 23 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Backfire DEFINITION The fuel ignites in the intake manifold or in the exhaust system making loud popping noise Preliminary Check e Refer to Important Preliminary Checks Ignition System Checks e Check for the proper ignition coil output voltage using the spark tester J26792 or the eguivalent Check the spark plug wires by connecting an ohmmeter to the ends of each wire in question If the meter reads over 30 000 ohms replace the wires Check the connection at each ignition coil Check for deteriorated spark plug wire insulation Check the spark plugs The correct spark plugs are R42LTS Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Engine Mechanical Check Check the engine for the following Improper valve timing Engine compression Manifold vacuum leaks Intake manif
18. throttle body assembly which is then connected to the intake manifold ofthe engine The Throttle body maintains control of engine speed by increasing or decreasing the open ing angle of the throttle blade in the throttle body bore thus increasing or decreasing the fuel air mixture to the engine The throttle blade shaft is connected to a spring loaded cable connector which is connected to the foot pedal in the oper ator s compartment The shaft incorporates a return spring to insure the blade position returns to idle when the operator removes his foot from the pedal Also attached to the throttle shaft is a Throttle Position Sensor TPS which provides a signal to the ECM to indicate the throttle blade angle for speed control and load control as well as emission control On the end opposite the TPS is the Foot Pedal Position FPP sen sor which operates the foot pedal override command Also mounted to the throttle control device is an integrated electronic governor The throttle control is maintained by a foot pedal located in the operator s compartment and con nected to the throttle control device by a cable The governor is controlled by the ECM and has no external adjustments When the ECM determines load adjustment or maximum en gine speed has been achieved the governor overrides the foot pedal and corrects the throttle plate position Also mounted on throttle body assembly is the Fuel Trim Valve The 15 12 v
19. 2 Are any other DTCs present Visually and physically check the following items Go to Step 7 Go to Step 4 The air intake duct for being collapsed or restricted The air filter for being plugged The HO2S sensor installed securely and the wire leads not contacting the exhaust manifold or ignition wires ECM grounds for being clean and tight Refer to Section 1C Engine Electrical Power and Ground Distribution Fuel System Diagnostics Refer to Section 1B Fuel System Diagnostics Was a repair made Go to Step 7 Go to step 4 Key ON Engine running Battery Go to Step 5 Repair the Using a DVOM back probe the HO2S sensor voltage circuit as connector heater circuit pin C for positive and D for necessary negative check for voltage Refer to Do you have voltage Wiring Repairs in Engine Electrical Key OFF Repair the Go to Step 6 Disconnect HO2S sensor wire harness connector circuit as Disconnect ECM wire harness connector necessary Refer to REY UN Wiring Repai g Repairs Using a DVOM check for voltage at HO2S in Engine connector signal pin B and engine ground Electrical Do you have voltage 1 3 e Diagnose any other DTC codes before proceeding with this chart Have any other DTC codes been detected diagnosed and repaired e Replace HO2S sensor Go to Step 7 Is the replacement complete IMPCO Technologies Engine Service Manual 111 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Rem
20. 6 Check for any DTC codes and clear Verify engine is in closed loop and no MIL lights are present THREE WAY CATALYTIC CONVERTER MUFFLER REPLACEMENT 1 Remove the TWC muffler using the OEM end product processes Installation Procedure IMPORTANT e The Three Way Catalytic converter is specifically designed to meet the emission control of the certi fied engine Use only the OEM specified parts 2 Install the TWC muffler using the OEM end product processes 3 Start engine 4 Check for any DTC codes and clear 5 Verify engine is in closed loop and no MIL lights present 12 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine RESTRICTED EXHAUST SYSTEM DIAGNOSIS EXHAUST SYSTEM DESCRIPTION The emission certified engine has been designed and calibrat ed to meet the emission standards in effect for 2004 To help meet the emission requirements the vehicle has been equipped with a Three Way Catalytic TWC muffler The catalyst muffler is a three way catalyst sound damping and spark ar resting unit Besides controlling the noise created from the combustion process and preventing sparks from escaping from the exhaust system the most important function is treat ing the exhaust gases which are created from the combustion process The three way catalyst consists of a honeycomb coated with a mixture of platinum palladium and rhodium The hot gases flow through the catalyst sections where an
21. A more frequent replacement of the filter may be required if the equipment operates in a dusty or dirty environment Fuel System Operation 1A2 FUEL RAIL AND PRESSURE REGULATOR The fuel flows from the fuel filter to the fuel rails where the fuel is regulated During engine operation the regulator maintains the proper amount of fuel pressure to the top of the injector During lower RPM operation excess fuel at the top of the injector is bypassed and returned to the fuel tank for recirculation The Fuel pressure regulator has no adjustments and is inte grated into the fuel rail assembly The fuel rail also contains a Schrader valve which is utilized to test the regulated pres sure of the fuel system Pressure Test Port Pressure Regulator Fuel Rail Assy Figure 2 Gasoline Fuel Rail Assembly FUEL INJECTOR The fuel supply is maintained on the top of the injector by the fuel pressure regulator The injector is fed a pulse signal through the wire harness which causes the injector to open During regular operating conditions the ECM controls the opening and duration of opening of the injector During lower RPM operation the injector signals or pulses are less frequent then when the engine is operating at higher RPMs The certified engine has been calibrated to deliver the precise amount of fuel for optimum performance and emission con trol THROTTLE CONTROL DEVICE Drive By Cable Engine speed control is maint
22. Compare the engine coolant temperature with the ambient air temperature on a cold engine IF the coolant temperature reading is more than 5 degrees greater or less than the ambient air temperature ona cold engine check for high resistance in the coolant sensor circuit Refer to DTC 111 Check the Crankshaft Position CKP sensor Check the Throttle position TPS sensor Fuel System Checks Check for fuel pump electrical circuit Verify proper fuel pump pressure Verify proper Fuel rail pressure Refer to the Gasoline Fuel System Diagnosis Check Electrical connections at the injectors Ignition System Checks Check for the proper ignition voltage output with J 26792 or the equivalent Verify that the spark plugs are correct use 42 5 Check the spark plugs for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits e Check for bare or shorted ignition wires e Check for moisture in the distributor cap if applicable e Check for loose ignition coil connections Important If the engine starts but then immediately stalls Crankshaft Position CKP Check for improper gap debris or faulty connections Engine Mechanical Checks Check for the following Vacuum leaks Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes Ref Check the intake and exhaust manifolds for casting flash 20 IMPCO Technologies
23. Engine Control Module Air Cleaner Distributor Timing Oil Pressure Crankshaft Sensor Catalytic Muffler Figure 1 Typical Fuel System Schematic 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Fuel System Operation 1A1 DESCRIPTION AND OPERATION OF THE FUEL SYSTEMS PROPANE FUEL SYSTEM The primary components of the propane fuel system are the fuel storage tank low pressure regulator LPR fuel mixer module with throttle control device electric fuel lock off so lenoid engine control module ECM fuel trim valve FTV pressure trim valve PTV and Three Way Catalytic TWC converter The system operates at pressures which range from 355 60 mm 14 0 inches of water column up to 21 5 BAR 312 psi Figure 1 Typical Fuel System Schematic LPG FUEL TANK Propane is stored in the fuel tank as a liquid The approxi mate pressure of the fuel in the tank is 16 5 bar 240 psi when the tank is full at an ambient temperature of 27 C 81 The boiling point temperature at which the liquid fuel becomes vapor is approximately 40 40 F When the fuel changes from liquid to vapor the fuel expands and creates pressure inside the tank When the tank service valve is opened the pressure inside the tank forces the liquid fuel out though the pick up tube located near the bottom of the fuel cylinder Because the Propane is stored under pressure the tank is eguipped with a safety va
24. Injectors System will be lean if an injector driver or driver circuit fails open The system will also be lean if an injector fails in a closed manner or is dirty Fuel Pressure Low fuel pressure faulty fuel injector or damaged fuel pump assembly can cause fuel system to run lean Exhaust Leaks If there is an exhaust leak outside air can be pulled into the exhaust and past the 02 sensor causing a false lean condition Fuel Quality Contaminated or spoiled fuel can cause the fuel system to be lean Ground Problem ECM grounds must be good battery or engine ground 104 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 se _ Ye No e Perform the On Board OBD System Check mE Go to ET 3 Goto Step 2 Visually and physically check the following items Go to Step 8 Go to Step 4 The air intake duct for being collapsed or restricted The air filter for being plugged The HO2S sensor installed securely and the wire leads not contacting the exhaust manifold or ignition wires ECM grounds for being clean and tight Refer to Section 1C Engine Electrical Power and Ground Distribution Fuel System Diagnostics Refer to Section 1B Fuel System Diagnostics Was a repair made e Diagnose any other DTC codes before proceeding Go to Step 8 Go to step 4 Have any other DTC codes been detected diagnosed and repaired Key OFF Repair the Go to Step 6 Disconnect HO2S
25. SECTION 1A2 GASOLINE FUEL SYSTEM OPERATION IMPCO Technologies Engine Service Manual 1 1A2 Fuel System Operation 4 3 liter Emission Certified GM Engine IMPCO 4 3 LITER MPFI FUEL SYSTEM VA VZ FUEL MIXTURE 5 FRESH AIR Z EXHAUST GASES GASOLINE RETURN GASOLINE FUEL PRESSURE Gasoline Fuel Pump k z GASOLINE FUEL PUMP PRESSURE Fuel Filter i fi E 1 Pressure ngine Control Module Air Cleaner o 5 4 TPS H Throttle Bod i TTMAP Y EPP AN gt Speed 7 H control motor q H Manifold Injector N MPFI System Distributor Timing Crankshaft FA Sensor RPM Oil Pressure ENGINE Catalytic Muffler Figure 1 Gasoline Multi Port Fuel Injection System 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine GASOLINE MULTI POINT FUEL INJECTION SYSTEM MPFI The primary components of the Gasoline Multi Point Fuel Injection MPFI fuel system are the gasoline fuel tank elec tric fuel pump fuel filter fuel rails fuel pressure regulator fuel injector O2 sensor engine control unit and three way catalytic muffler GASOLINE FUEL STORAGE TANK T
26. e Check for continuity between HO2S sensor connector signal pin B and ECM connector HO2S signal pin 55 Do you have continuity between them Replace HO2S Sensor Is the replacement complete Go to Step 9 Diagnostic Trouble Codes 1C4 Go to OBD System Check Section Go to Step 3 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Check System Power Relay circuit Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical IMPCO Technologies Engine Service Manual 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Inspect ECM connector pins 49 and 55 for Repair the Go to Step 7 damage corrosion or contamination circuit as Inspect HO2S connector terminals A B C and D necessary for damage corrosion or contamination Refer to Wiring Repairs Did you find a problem in Engine Electrical Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the tes
27. etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 261 check for any stored codes Does the engine operate normally with no stored codes 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 262 System Voltage High ECM BK GROUND BK 20 RIT 22 VBAT RT 23 Conditions for Setting the DTC System Voltage to ECM Check Condition Cranking or Running Fault Condition Switched battery voltage at ECM greater than 18 volts for 3 seconds MIL On for active fault and for 5 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The battery voltage powers the ECM and must be measured to correctly operate injector drivers trim valves and ignition coils This fault will set if the ECM detects voltage greater than 18 volts for 3 seconds at anytime the engine is cranking or running The adaptive learn is disabled The ECM will shut down with internal protection if the system voltage exceeds 26 volts The ECM fuse will then open 118 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC
28. is mounted in the exhaust system downstream of the engine The HEGO is used to measure the amount of oxygen present in the ex haust stream and communicate that to the ECM via an elec trical signal The amount of oxygen present in the exhaust stream indicates whether the fuel air ratio is to rich or to lean If the HEGO sensor signal indicates that the exhaust stream is to rich the ECM will decrease or lean the fuel mixture by reducing the signals to the injectors during engine operation if the mixture is to lean the ECM will richen the mixture or increase the pulse to the injectors The ECM continuously monitors the HEGO sensor output if a rich or lean condition is present for an extended period of time and the ECM cannot correct the condition the ECM will set a diagnostic code and turn on the MIL light in the dash A CAUTION The Heated Exhaust Gas Oxygen Sensor HEGO is an emissions control component If the HEGO fails to operate replace only with an OEM replacement part The HEGO sensor is sensitive to silicone and silicone based products and can become contaminated Avoid using silicone sealers or hoses treated with silicone lubricant in the air stream or fuel sup ply lines Figure 6 Heated Exhaust Gas Oxygen Sensor Hego IMPCO Technologies Engine Service Manual 5 1A2 Fuel System Operation 4 3 liter Emission Certified GM Engine 6 ET ENGINE N Output
29. 11 Rotate the LPR to 90 so that the outlet fitting is pointing down into the receptacle and drain the LPR 12 Inspect the secondary chamber for any large dried particles and remove 13 Remove the receptacle and reinstall the LPR with the two retaining bolts and tighten to specifications 14 Reinstall the outlet fitting and secure with the previously removed locking pin 15 Reconnect the PTV electrical connection push connector until lock Click pull on the connector to ensure it is locked connect the vacuum line 16 Reconnect the outlet hose and secure the hose clamp 17 Reinstall the fuel inlet line and tighten connection to specification 18 Slowly open the manual service valve IMPORTANT The fuel cylinder manual valve contains an Excess Flow Check Valve open the manual valve slowly to prevent acti vating the Excess Flow Check Valve 19 Check for leaks at the inlet and outlet fittings using a soapy solution or an electronic leak detector if leaks are detected make repairs Check coolant line connections to ensure no leaks are present 20 Start engine recheck for leaks at the regulator 21 Dispose of any drained material in safe and proper man ner AIR FUEL MIXER THROTTLE CONTROL DEVICE MAINTENANCE AND INSPECTION IMPORTANT The Air Fuel Mixer components have been specifically de signed and calibrated to meet the fuel system reguirements of the emission certified engine The mixer
30. Assemble brushes and related parts to field frame as follows A Assemble brushes to brush holders Attach ground wire to grounded brush and field lead wire to insulated brush B Assemble insulated and grounded brush holders together with V spring Position as a unit and install support pin Push holders and spring to bottom of support and rotate spring to engage center of V spring in slot of support 2 Assemble overrunning clutch assembly to armature shaft as follows figure 4 8 A Lubricate drive end of armature shaft with SAE 10 oil Install bearing plate washer and clutch assembly onto armature shaft with pinion outward C Slide retaining collar onto shaft with cupped surface facing end of shaft away from pinion D Drive snap ring onto shaft and slide down into groove E Assemble the thrust collar on shaft with shoulder next to snap ring F Place thrust collar and retaining collar next to snap ring Using two pliers sgueeze both until snap ring is forced into retainer 3 Place four or five drops of light engine oil in drive housing bushing Slide armature and clutch assembly into place while engaging shift lever with clutch Install center bearing attach ing screws and tighten securely 4 Position field frame over armature Care fully apply liquid neoprene between frame and drive housing Use caution to prevent damage to brushes 5 Place four or five drops of light engine oil in bushing in
31. Certified GM Engine DEFINITION A surging or jerking that follows engine speed usually more pronounced as the engine load increases which is not normally felt above 1500 RPM The exhaust has a steady spitting sound at idle low speed or hard acceleration for the fuel starvation that can cause the engine to cut out Ignition System Checks Start the engine Wet down the secondary ignition system with water from a spray botile and look listen for arcing or misfiring as you apply water Check for proper ignition output voltage with spark tester 26792 Check for a cylinder misfire Verify that the spark plugs are correct for use with LPG R42LTS Remove the spark plugs in these cylinders and check for the following conditions Insulation cracks Wear Improper gap Burned electrodes Heavy deposits Visually Physically inspect the secondary ignition for the following Ignition wires for arcing cross firing and proper routing Ignition coils for cracks or carbon tracking Engine Mechanical Checks Perform a cylinder compression check Check the engine for the following Improper valve timing Bent pushrods Worn rocker arms Worn camshaft lobes Broken or weak valve springs Check the intake and exhaust manifold passages for casting flash Fuel System Checks Check the fuel system plugged fuel filter low fuel pressure etc Refer to LPG Fuel System Diagnosis Check the condition of the wiring to the low pressure lock off solen
32. Check the ECM ground for being clean tight and in its proper location Check the vacuum hoses for splits kinks and proper connections Check thoroughly for any type of leak or restriction Check for air leaks at all the mounting areas of the intake manifold sealing surfaces Check for proper installation of the mixer module assembly Check for air leaks at the mixer assembly Check the ignition wires for the following conditions Cracking Hardness Proper routing Carbon tracking Check the wiring for the following items Proper connections pinches or cuts The following symptom tables contain groups of possible causes for each symptom The order of these procedures is not important If the scan tool readings do not indicate the problems then proceed in a logical order easiest to check or most likely to cause first 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Intermittent Checks l DEFINITION The problem may or may not turn ON the Malfunction Indicator Lamp MIL or store a Diagnostic Trouble Code DTC Preliminary Checks Refer to Important Preliminary Checks Do not use the DTC tables If a fault is an intermittent the use of the DTC tables may result in the replacement of good parts Faulty Electrical Connections or Faulty electrical connections or wiring can cause most intermittent problems Wiring Check the suspected circuit for t
33. Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM has checks that must be satisfied each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 138 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 555 RTI 2 Loss Sep Vawis Ye Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code Does 555 reset with the engine idling Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribu
34. Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Exhaust System Checks e Check the exhaust system for a possible restriction Inspect exhaust system for damaged or collapsed pipes Inspect muffler for signs of heat distress or for possible internal failure e Check for possible plugged catalytic converter Refer to Restricted Exhaust System Diagnosis IMPCO Technologies Engine Service Manual 21 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Cuts Out Misses DEFINITION A surging or jerking that follows engine speed usually more pronounced as the engine load increases which is not normally felt above 1500 RPM The exhaust has a steady spitting sound at idle low speed or hard acceleration for the fuel starvation that can cause the engine to cut out Preliminary Checks e Refer to Important Preliminary Checks Ignition System Checks e Start the engine e Wet down the secondary ignition system with water from a spray bottle and look listen for arcing or misfiring as you apply water Check for proper ignition output voltage with spark tester J 26792 Check for a cylinder misfire Verify that the spark plugs are correct use RA2LTS Remove the spark plugs in these cylinders and check for the following conditions e Insulation cracks e Wear Improper gap Burned electrodes Heavy deposits Visually Physically inspect the secondary ignition for the following I
35. Heated Exhaust Gas Oxygen Sensor HEGO is mounted in the exhaust system downstream of the engine The HEGO is used to measure the amount of oxygen present in the ex haust stream and communicate that to the ECM via an elec trical signal The amount of oxygen present in the exhaust stream indicates whether the fuel air ratio is to rich or to lean Ifthe HEGO sensor signal indicates that the exhaust stream is to rich the ECM will decrease or lean the fuel mixture dur ing engine operation if the mixture is to lean the ECM will richen the mixture The ECM continuously monitors the HEGO sensor output if a rich or lean condition is present for an extended period of time and the ECM cannot correct the condition the ECM will set a diagnostic code and turn on the MIL light in the dash Figure 11 Heated Exhaust Gas Oxygen Sensor HEGO IMPCO Technologies Engine Service Manual 7 1A1 Fuel System Operation 4 3 liter Emission Certified GM Engine 7 ENGINE Output Input PTVOR Exhaust FTV pulses Gas Oxygen increases or Sensor decreases HEGO to fuel delivery ECM to the engine ECM Calaculates K the change and commands P OR FTV signals decrease Figure 12 Propane Closed Loop Control Schematic 8 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Fuel System Operation 1A2
36. Input Injector Heated sud or nn decreases mad fuel delivery HEGO to to the ECM engine x e ECM Calculates amp the change and commands injector signal to increase or decrease Figure 7 Gasoline Closed Loop Control Schematic IMPCO Technologies Engine Service Manual SECTION 1B1 LPG SYSTEM DIAGNOSIS IMPCO Technologies Engine Service Manual 1 1B1 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine LPG Fuel System Diagnosis Electric Lock x Pressure Trim Valve Secondary Test Port Primary Test Port Figure 1 Low Pressure Regualtor Assembly Fuel System Description The Engine Control Module ECM receives information from various engine sensors in order to control the operation of the fuel control solenoid valves and the low pressure lock off LPL solenoid The LPL solenoids prevent fuel flow unless the engine is cranking or running LPG is stored in the tank and delivered under pressure to the system as a liq uid During key on the LPL receives a two 2 second prime pulse from the ECU which allows LPG to flow from the tank through fuel filter and fuel lines to the low pressure regulator LPR at pressures up to 21 5 BAR 312 psi In the LPR the fuel is vaporized and the pressure reduced in two stages The first stage reduces the pressure to approxi mately 20 68 kilopascals 3 0 psi The second stage reduces the
37. LOW PRESSURE REGUALTOR LPR The LPR is a combination vaporizer pressure regulating de vice The LPR is a negative pressure two stage regulator that is normally closed when the engine is not running When the engine is cranking or running a partial vacuum is created in the fuel line which connects the regulator to the mixer This partial vacuum opens the regulator permitting fuel to flow to the mixer Propane fuel enters the primary port ofthe LPR and passes through the primary jet and into the primary exchanger cham ber As the propane passes through the heat exchanger the fuel expands and creates pressure inside the chamber The pressure rises as the fuel expands when the pressure rises above 10 34 kpa 3 5 psi sufficient pressure is exerted on the primary diaphragm to cause the diaphragm plate to pivot and press against the primary valve pin thus closing off the flow of fuel This action causes the flow of fuel into the regula tor to be regulated When the engine is cranking sufficient vacuum will be introduce into the secondary chamber from the mixer drawing the secondary diaphragm down onto the spring loaded lever and opening the secondary valve allow ing vaporized fuel to pass to the mixer Increased vacuum in the secondary chamber increases the downward action on the secondary lever causing it to open wider allowing more fuel to flow to the mixer The regulator utilized on this emission certified engine is equipped with a unique
38. Loop An operational mode during which control module memory information is used to determine air fuel ratio injec tion timing etc as opposed to actual oxygen sensor input Orifice A port or passage with a calibrated opening designed to control or limit the amount of flow through it Oscilloscope An instrument that converts voltage and frequency readings into traces on a cathode ray tube also see Cathode Ray Tube Oxides of Nitrogen Chemical compounds of nitrogen bonded to various amounts of oxygen Nox A chief smog forming agent Oxygen Sensor An automotive fuel system that produces a signal in accordance with the oxygen content of the exhaust gas See Lambda Sensor Oxygenate MTBE ethanol and methanol Oxygenates are added to gasoline to increase the oxygen content and therefore reduce exhaust emissions Ozone A radical oxygen module O3 that is found in the upper atmosphere and filters out ultraviolet radiation from the sun Ground level ozone is formed by Nox during the formation of photochemical smog Particulates Microscopic pieces of solid or liquid substances such as lead and carbon that are discharged into the atmosphere by internal combustion engines Positive Crankcase Ventilation PCV An automotive emission control system designed to reduce hydrocarbon emissions by routing crankcase fumes into the intake manifold rather than to the atmosphere Pressure Differential The differential between atmospheric pres
39. Open Circuit 1 With continuity meter place one lead on each end of field coils insulated brush and field connector bar figure 4 6 2 If meter does not move field coils are open and must be replaced Test For Ground IMPORTANT sure that positive brushes and leads do not contact field frame assembly during test or false reading will result 1 With continuity meter place one lead on field connector bar and other lead on grounded brush figure 4 7 2 If meter needle moves field coils are grounded and must be replaced 4 3 liter Emission Certified GM Engine Starter 1C5 SAW BLADE GROWLER 22664 012 Figure 4 5 Testing Armature for Short Circuits Figure 4 7 Testing Field Coil for Grounded Circuit LOOSE ELECTRICAL CONNECTIONS If an open soldered connection of armature to commutator leads is found during inspection resol der it with resin flux IMPORTANT Never use acid flux on electrical connections Turning the Commutator When inspection shows commutator roughness clean as follows 1 Turn down commutator in a lathe until thor oughly cleaned 2 Recheck armature for shorts as outlined 22664 011 Figure 4 6 Testing Field Coils for Circuit IMPCO Technologies Engine Service Manual 5 1C5 Starter 6 STARTER MOTOR ASSEMBLY Figure 4 8 After all parts are thoroughly tested and inspected and worn or damaged parts replaced reassemble starter as follows 1
40. Pressure Trim Valve PTV which is directly mounted to the regulator This solenoid is a 12 volt normally closed solenoid The function of this solenoid 4 IMPCO Technologies Engine Service Manual is to regulate a specific amount of venture vacuum to the at mospheric side of the secondary diaphragm By introducing vacuum to the top side of the secondary diaphragm during regulator operation the amount of fuel being delivered to the mixer can be trimmed or reduced to allow for correction to the air fuel ratio for closed loop fuel control The solenoid receives a reference signal from the ECM which causes the solenoid to be pulsed fast or slow depending on the amount of fuel to be trimmed The LPR is an emission control de vice Components inside the regula tor are specifically calibrated to meet the engine emissions requirements and should never be disassembled or rebuilt If the LPR fails to operate re place with an OEM replacement part Figure 5 Low pressure regulator AIR FUEL MIXER The air valve mixer is an air fuel metering device and is completely self contained The mixer is an air valve design utilizing a relatively constant pressure drop to draw fuel into the mixer from cranking to full load The mixer is mounted in the air stream ahead of the throttle control device When the engine begins to crank it draws in air with the air valve covering the inlet negative pressure begins to build This negative pressure signa
41. Repairs in Engine 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 emove all test equipment except the DST ystem OK Connect any disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 612 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 149 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 631 TPS 1 Signal Voltage High LT GRN RED 5 volts PPL LT BLUE Signal BLK LT GRN Sensor Ground Conditions for Setting the DTC Throttle Position Sensor 1 Check Condition Cranking or Running Fault Condition TPS sensor voltage exceeds 4 8 MIL On during active fault 9 Engine Shut Down Circuit Description The Electronic Throttle has two counter acting Throttle Position Sensors Two sensors are used for improved safety and redundancy The Throttle Position sensor uses a variable resistor to determine signal voltage based on throttle plate position and is connected to the throttle shaft Less opening results in lower voltage and greater opening in higher voltage The TPS value is used by the ECM to determi
42. Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 112 check for any stored codes Does the engine operate normally with no stored codes e Check for continuity between TMAP sensor Go to step 7 connector signal circuit pin B and engine ground Repair the Do you have continuity circuit as necessary Refer to Wiring Repairs in Engine Electrical 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 113 IAT Higher Than Expected 1 Bosch amp TMAP BLK LT GRN LT GRN RED TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition Intake Air Temperature greater than 210 degrees F and engine RPM greater than 1000 MIL Will flash at 2 Hz twice per second during active fault Adaptive Disabled during active fault Closed Loop Enabled Power Derate Level 1 Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the a
43. Turn the engine OFF 2 Disconnect the ECU connector C001 3 Disconnect the PTV electrical connector 4 Check the PTV ground circuit terminal A for continuity to the ECU connector pin number 2 5 Check the PTV ground circuit in Terminal A for short to ignition power or ground Was a problem found Go to Step Go to Step 1 11 Using the DVOM measure the resistance at the PTV terminals Was the resistance measured within specifi cation 16 0 24 0 Go to Step 17 Go to Step 19 1 Connect the negative lead of the DVOM to battery negative 2 Using the positive lead of the DVOM Back probe Pin B at the FTV connector 12 6 V to 15 1 V Was the FTV voltage within the specified range Go to Step 14 Go to Step 13 8 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine LPG Fuel System Diagnostics 1B1 1 Turn the engine OFF 2 Disconnect the ECU connector C001 3 Disconnect the FTV electrical connector 4 Check the FTV ground circuit terminal A for continuity to the ECU connector pin 2 5 Check the FTV ground circuit in Terminal A for short to ignition power or ground 14 Using the DVOM measure the resistance at the FTV terminals 16 0 24 0 Was the resistance measured within specifi cation Go to Step Go to Step Replace the Engine Control Unit ECU Refer to Engine Control Unit ECU replace ment 17 Check the vacuum hose to the PTV for kinks obstruction or leakage 18 Check the fue
44. Yellow Injector 4 IMPCO Technologies Engine Service Manual 43 INJECTOR 5 CONNECTOR C032 ac Orange Lt Blue Fuel Trim Valve Brown White Injector 5 44 IMPCO Technologies Engine Service Manual INJECTOR 6 CONNECTOR C033 Orange Lt Blue Fuel Trim Valve Injector 6 IMPCO Technologies Engine Service Manual 45 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi 46 IMPCO Technologies Engine Service Manual SECTION 1C4 DIAGNOSTIC TROUBLE CODES IMPCO Technologies Engine Service Manual 1 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DESCRIPTION OF ECM BASED DIAGNOSTICS DEFINITION OF TERMS Active Gov Mode AL AL Mult Analog Batt BP CHT CL CL Mult Closed Loop DBW DTC ECT ECM EGO FPP HO2S IAT IVS MAP MAT MIL ms Open Loop PSIA RAM TPS Speed is governed by one oftwo modes Isochronous which maintains an exact speed or Droop which allows speed to drop a predetermined amount based on current engine load Adaptive Learn Adaptive Learn Multiplier The adaptive learn multiplier is a correction to the fuel delivery which is ex pressed as a percentage and stored in the ECM s RAM 0 to 5 volt or 0 to 12 volt signals Battery Voltage Barometric Pressure The pressure of the outside air Cylinder Head Temperature Closed Loop Closed Loop Multiplier The closed loop multiplier is a fast acting adjustment t
45. a honeycomb coated with a mixture of platinum palladium and rhodium The hot gases 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine flow through the catalyst sections where an oxidation and re duction reactions take place These chemical reactions reduce the amount of CO HC and NOX in the engines exhaust The Exhaust gas then flows through the outlet Figure 4 Three Way Catalytic Converter ENGINE CONTROL UNIT To obtain maximum effect from the catalyst and accurate control of the air fuel ratio the emission certified engine is equipped with an onboard computer or Engine Control Unit ECM The ECM is a 32 bit controller which receives in put data from sensors fitted to the engine and fuel system and then out puts various signals to control engine operation One specific function of the controller is to maintain closed loop fuel control Closed loop fuel control is accomplished when the exhaust gas oxygen sensor EGO mounted in the exhaust system sends a voltage signal to the controller The controller then calculates any correction that may need to be made to the air fuel ratio The controller then changes the amount of fuel being delivered to the engine by changing the pulse frequency to the injector The controller also performs diagnostic functions on the fuel system and notifies the opera tor of malfunctions by turning on a Malfunction Indicator Light MIL mounted in the dash Malfuncti
46. and the MIL will be on 60 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 132 MAP Low Voltage Motorola Sep Action Vale s Did you perform the On Board OBD System Check Key On Engine running DSC Diagnostic Scan Tool connected in System Data Mode Does DST display MAP voltage of 0 05 or less with the engine idling Key OFF Disconnect the TMAP sensor from the wiring harness Jumper the 5 volt reference pin C and MAP signal circuit pin D together Key ON Does the DST display MAP voltage of 4 5 volts or greater e Inspect TMAP connector pins for corrosion contamination or mechanical damage Any problems found Key OFF Disconnect ECM connector Check for continuity between TMAP sensor connector signal pin D and ECM MAP signal pin 33 Do you have continuity between them e Check for continuity between TMAP sensor connector 5 volt supply signal pin C and ECM 5 volt supply pin 50 Do you have continuity between them e Check for continuity between TMAP sensor connector ground pin A and ECM sensor ground pin 49 Do you have continuity between them Go to OBD System Check Section Go to Step 3 Intermittent problem Go to m 2 section Go to Step 4 Go to step 8 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Go to Step 6 Go to step 7 Go to step 1 IMPCO Technologies
47. as necessary Refer to Wiring Repairs in Engine Electrical IMPCO Technologies Engine Service Manual 35 Inspect ECM connector pin 37 for damage corrosion or contamination Did you find a problem Key OFF Go to Step 6 Go to Step 5 Disconnect oil pressure switch harness connector C005 Jumper the pressure switch LT GRN BLK wire to engine ground Clear DTC 115 Start engine let idle for at least one minute with ECT over 160 degrees F Increase engine speed above 1300 RPM Does DTC 115 reset e Replace ECM e Is the replacement complete 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 115 check for any stored codes Does the engine operate normally with no stored codes 36 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 37 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 121 ECT High Voltage A pi ee Sensor Ground Conditions for Setting the DTC Engine Coolant Temperature Hm C
48. catalyst and accurate control of the air fuel ratio the emission certified engine is equipped with an onboard computer or Engine Control Module ECM The ECM is a 32 bit controller which re ceives input data from sensors fitted to the engine and fuel system and then outputs various signals to control engine operation One specific function of the controller is to maintain closed loop fuel control Closed loop fuel control is accomplished when the Heated Exhaust Gas Oxygen sensor HEGO mounted in the exhaust system sends a voltage signal to the controller The controller then calculates any correction that may need to be made to the air fuel ratio The controller then outputs signals to PTV or the FTV or both mounted in the fuel system to change the amount of fuel being delivered from the regulator or mixer or to the engine 4 3 liter Emission Certified GM Engine Fuel System Operation 1A1 LPG ECM INPUTS OUTPUTS 02 Sensor z Throttle Position 9 RPM Ming ee ENGINE CONTROL MODULE Oil Pressure Coolant Temperature Air Temperature 3 Manifold Absolute Pressure 39 Battery Pressure Trim Valve Fuel Trim Valve Electric Lockoff Valve Governor Speed Control Timing Ignition lt
49. connector Using a DVOM check for continuity between ECT sensor ground pin B and ECM connector pin 49 Do you have continuity between them Inspect ECM connector pins 31 and 49 for damage corrosion or contamination Did you find a problem 11 e Replace ECM Is the replacement complete Disconnect ECM wire harness connector Using ADVOM check for continuity between ECT connector signal pin A and ECM connector terminal 31 Do you have continuity between them circuit as necessary Refer to Wiring Repairs in Engine Electrical System OK Go to OBD System Check damage corrosion or contamination Did you find a problem Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 121 check for any stored codes Does the engine operate normally with no stored codes Inspect ECM connector pins 31 and 49 for Repair the Go to Step 11 40 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 41 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 122 ECT Low Voltage Sensor Ground ECM Conditions for Setting the
50. connector e Check for continuity between TMAP sensor connector pin D and ECM connector pin 33 Do you have continuity between them e Check for continuity between TMAP sensor connector 5 volt supply pin C and ECM connector pin 50 Do you have continuity between them Go to Step 6 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Go to step 7 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Go to step 1 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical IMPCO Technologies Engine Service Manual 73 e Check for continuity between TMAP sensor connector ground pin A and ECM connector pin 49 Do you have continuity between them e Inspect TMAP connector and wire harness Repair the circuit Go to step 5 connector terminals for corrosion contamination as necessary or mechanical damage Refer to Wiring Any problems found Repairs in Engine Electrical 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove Jumper that was installed during step 3 Go to Step 9 Go to step 13 Probe TMAP connector signal circuit D with a test light connected to battery voltage Does the DST display BP pressure of 16 00 psia or greater Disconnect ECM connector Check for continuity between TMAP sensor connector pin C and ECM connector pin 50 Do you have continuity between them Check for continuity between TMAP
51. etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 144 check for any stored codes Does the engine operate normally with no stored codes Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 144 check for any stored codes Does the engine operate normally with no stored codes 86 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 87 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 145 Camshaft Sensor Noise Dist Cam Sensor 5 volts Conditions for Setting the DTC Camshaft position sensor Check Condition Cranking or Running Fault Condition One invalid cam re sync MIL On for active fault and for 10 seconds after active fault Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Circuit Description The camshaft positio
52. for DTC 112 IAT Low Voltage IMPCO Technologies Engine Service Manual 31 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 114 IAT Higher Than Expected 2 Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition Intake Air Temperature greater than 220 degrees F and engine RPM greater than1000 MIL On for active fault and for 15 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Engine Shut Down Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold ofthe engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The IAT is a calculated value based mainly on the IAT sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow This fault will set ifthe Intake Air Temperature is greater than 220 degrees F and engine RPM is greater than 1000 The MIL light will be on during this active fault and the engine will shut down 32 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Eng
53. from the liquid components of natural gas stripped out before the gas enters the pipeline and the lightest hydrocarbons produced during petroleum refining Octane level is 107 LPG Liquified Petroleum Gas M85 A blend of gasoline and methanol consisting of 85 methanol and 15 gasoline Measurements of Pressure 1 PSI 2 06 Hg mercury 27 72 H2O water column At sea level atmospheric pressure is 29 92 Hg Methanol Known as wood alcohol a light volatile flammable alcohol commonly made from natural gas Misfire Failure of the air fuel mixture to ignite during the power stroke Mixer Fuel introduction device that does not include a throttle plate MPFI Multi Point Fuel injection A fuel injection system that uses one injector per cylinder mounted on the engine to spray fuel near the intake valve area of combustion chamber MTBE Methyl Tertiary Butyl Ether Oxygenate add to gasoline to reduce harmful emissions and to improve the octane rating Multi fuel System A motor fuel system designed to operate on two different fuels such as LPG and gasoline Natural Gas A gas formed naturally from buried organic material composed of a mixture of hydrocarbons with methane being the dominant component Natural Gas Vehicle Nox See Oxides of Nitrogen Octane Rating The measurement of the antiknock value of a motor fuel OEM Original Equipment Manufacturer the vehicle manufacturer Open
54. gases flow through the catalyst sections where an oxidation and reduction reactions take place These chemical reactions reduce the amount of CO HC and NOX in the engines exhaust The Exhaust gas then flows through the outlet During normal operation the exhaust system could become damaged Damage which reduces the flow of the exhaust gas will create increased back pressure in the engine Reduction in exhaust flow can result from crushed muffler outlets or melted catalyst brick inside the converter It may be necessary to measure the back pressure in the exhaust system To determine ifthe back pressure in the engine is correct use the following procedure Diagnostic Aids Tools Required 35314 Exhaust Back Pressure Gage Diagnostic Scan Tool e MPCO Fuel System diagnostic tool Check at Heated Exhaust Gas Oxygen Sensor HEGO Carefully remove the HEGO 2 Install exhaust backpressure test J35314 a in place of the HEGO 3 With the engine idling at normal operating temperature observe the exhaust system back pressure reading on te gage Reading should not exceed 8 6 kPa 1 25 psi 4 Increase engine speed to 2000 RPM and observe gage Reading should not exceed 20 7 kPa 3 psi 5 Ifthe back pressure at either speed exceeds specification a restricted exhaust system is indicated 6 Inspect the entire exhaust system for a collapsed pipe heat distress or possible internal muffler failure 7 lfthere are n
55. gt IMPCO Technologies Engine Service Manual 1C2 Wirina Scl ti 1 3 liter Emission Certified GM Engi 4 3L GASOLINE JUMP HARNESS ORANGE LT BLUE 16 1 BROWN LT BLUE 16 E BROWN ORANGE 16 BROWN WHITE 16 BROWN GREEN 16 D BROWN YELLOW 16 TAN LT BLUE 16 TAN LT BLUE 1 10 IMPCO Technologies Engine Service Manual ORANGE LT BLUE 16 CYL 1 CYL 2 BROWN LT BLUE 16 28 ORANGE LT BLUE 16 29 ORANGE LT BLUE 16 QRANGE LT BLUE 16 BROWN ORANGE 16 BROWN WHITE 16 k k CYL 3 CO30 CYL5 co3a2 BROWN GREEN 16 BROWN YELLOW 16 ORANGE LT BLUE 16 ORANGE LT BLUE 16 x age CYL4 CO31 CYL6 CO33 IMPCO Technologies Engine Service Manual 11 12 ECM CONNECTOR C001 INJ INJ 1 INJ2 AUX OUT 2A AUX ANA MAP FPP IAT ECT IVS AUX ANA PU1 POWER GROUND POWER GROUND ANA_RTN 5 VOLT REF VSW EGO 1 KNK KNK CRANK CRANK VBAT VBAT STARTER LOCKOUT FUEL LOCKOFF FUEL PUMP2 RELAY CONTROL TPSI TPS2 DBW DBW OIL PRESSURE TACH MIL AUX ANA PD2 AUX OUT 1A FUEL SELECT AUX ANA PU2 GOV SELECT GASEOUS TRIM CAN CAN RS 232 TX RS 232 RX COIL 1 INJ3 INJ4 INJ 5 INJ6 INJ7 INJ8 AUX OUT 3 IMPCO Technologies Engine Service Manual ORANGE BLUE 16 BROWN BLUE 16 BROWN GREEN 16 LT BLUE WHITE 18 TAN DK GREEN 18 LT GRN 18 DK BLUE 18 TAN 18 YELLOW GRAY 18 DK BLUE YELLOW 18 BLACK 16 BLACK 16 BLACK L
56. heavy ends may be a result of poor fuel quality contamination of the fuel supply chain or regional variation of the fuel make up If the build up of oil becomes significant this can affect the performance ofthe secondary diaphragm response The Recommended Maintenance Schedule found in this section recommends that the oil be drained periodically IMPORTANT Draining the regulator when the engine is warm will help the oils to flow freely from the regulator To drain the LPR use the following steps 1 Move the equipment to a well ventilated area and ensure no external ignition sources are present 2 Start the engine 3 With the engine running close the manual valve 4 When the engine runs out of fuel turn OFF the key when the engine stops and disconnect the battery negative cable IMPORTANT A small amount of fuel may still be present in the fuel line use gloves to prevent burns wear proper eye protection If liquid fuels continues to flow from the connections when loosened check to make sure the manual valve is fully closed 5 Slowly loosen the inlet fitting and disconnect 6 Loosen the hose clamp at the outlet hose fitting and remove the hose 7 Remove and retain the locking pin in the outlet fitting and remove the outlet fitting from the LPR 8 Disconnect PTV connection and disconnect the vacuum hose 9 Remove the two LPR mounting bolts and retain 10 Place a small receptacle in the engine compartment
57. ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 516 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 131 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 531 External 5V Ref Lower Than Expected LTGRN R Conditions for Setting the DTC External 5V reference Check Condition Cranking with battery voltage greater than 8 volts and engine running Fault Condition 5V reference voltage lower than 4 6 volts MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Circuit Description The External 5 Volt supply powers some of the sensors and other components in the system The accuracy of the 5 Volt supply is very important to the accuracy of the sensors and therefore controlled by the ECM The ECM monitors the 5 volt supply to determine if it is overloaded shorted or otherwise out of specification This fault will set if the 5 Volt reference is below 4 6 volts 132 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 531 External 5V Reference Lower Than Expected Value Ye Ne Did you perform
58. information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 132 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 59 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 132 MAP Low Voltage Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Manifold Absolute Pressure Check Condition Cranking or Running Fault Condition MAP voltage less than 0 05 Throttle Position greater than 2 and engine RPM less than 7000 MIL On for remainder of key on cycle Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Misc Fueling is based on RPM and TPS Limp Home Condition during this fault Circuit Description The Manifold Absolute Pressure sensor is a pressure transducer connected to the intake manifold It is used to measure the pressure of air in the manifold prior to induction into the engine The pressure reading is used in conjunction with other inputs to determine the airflow rate to the engine which determines the fuel flow rate This fault will set when the MAP reading is lower than the sensor should normally produce When this fault is set the Adaptive Learn will be disabled for the remainder ofthe key on cycle
59. misfire is occurring By monitoring 15 in the crankshaft rotation speed for linder the PCM is able to detect individual events misfire rate that is high enough can ree way catalytic converter TWC damage Ifunction indicator lamp MIL will flash ON and ien the conditions for catalytic converter gt are present ions for Running the DTC int If the start up engine coolant ture ECT is less than 7 C 20 F misfire is delayed until ECT is more than 21 If the start up ECT is more than 7 C 20 Jetection begins after a 5 second delay os P0101 P0102 P0103 P0116 P0117 118 P0128 P0335 P0336 P0341 P0343 500 P0502 P0503 P1114 P1115 P1121 122 P1220 P1258 P1336 or P1345 set fuel level is more than 10 percent engine speed is between 450 5 000 RPM system voltage is between 11 16 volts throttle position TP is steady within 2 percent 100 milliseconds ions for Setting the DTC M detects a deceleration in the crankshaft hat is characteristic of either an emission type or of a catalyst damaging type misfire 7820 Taken When the DTC Sets control module illuminates the malfunction cator lamp MIL on the second consecutive tion cycle that the diagnostic runs and fails control module records the operating iditions at the time the diagnostic fails The time the diagnostic fails the control module es this information in the Failure Records diagnostic r
60. not damaged or bent and will hold brushes against commu tator 4 Check brushes Replace if pitted or worn to one half their original length 5 16 in 8 mm or less 5 Check fit of armature shaft in bushing of drive housing Shaft should fit snugly Replace bushing if worn Apply SAE 20 oil to bushing before reassembly Avoid excessive lubrication IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine 6 Check fit of bushing in commutator end cap If bushing is damaged or excessively replace end cap assembly Apply SAE 20 oil to bushing before reassembly Avoid exces sive lubrication 7 Inspect armature commutator If rough or out of round turn down and undercut Inspect points where armature conductors join commutator bars for good firm connection Burned commutator bar usually is evidence of poor connection ARMATURE TESTS Figure 4 5 Test For Short Circuits Check armature for short circuits by placing on growler and holding hacksaw blade over armature core while rotating armature figure 4 5 If saw blade vibrates armature is shorted After cleaning between commutator bars recheck If saw blade still vibrates replace armature Test For Grounded Circuit 1 With continuity meter place one lead on armature core or shaft and other lead on commutator 2 If meter needle moves armature is ground ed and must be replaced FIELD COIL TESTS Figures 4 6 and 4 7 Test For
61. or outlet hoses when rein stalling Install hose clamps and set back on each hose Reinstall the coolant inlet hose to each fitting Reinstall the coolant outlet hose to each fitting Reset clamps Refill with coolant Start engine and check for coolant leaks IMPCO Technologies Engine Service Manual 1E1 Fuel System VAPOR HOSE REPLACEMENT 1 Using a hose clamp pliers disconnect both hose clamps 2 Remove the vapor hose form each fitting Installation Procedure IMPORTANT Vapor supply hose is specifically designed DO NOT use hose material or length other than the OEM specified parts Install hose clamps and set back on each hose Reinstall the vapor hose to each fitting Reset clamps nu Start engine and check for leaks BALANCE LINE HOSE REPLACEMENT Remove the clamp to the fitting at the mixer Remove small hose to check valve Remove and retain check valve Ru Remove the one 1 hose routing retaining bolt and re tain 5 Remove clamp at the LPR connection Installation Procedure IMPORTANT e Balance line hoses are specifically designed DO NOT use hose material or length other than the OEM specified parts e DO NOT mix the hoses when reinstalling e Install check valve in correct direction Arrow on check valve pointing toward mixer 7 Install hose clamps and set back on each hose 8 Reinstall the LPR hose end to the LPR fitting and set clamp 9 Install Check valve and set clamp Dire
62. oxi dation and reduction reactions take place These chemical re actions reduce the amount of CO HC and NOX in the engines exhaust The Exhaust gas then flows through the outlet During normal operation the exhaust system could become damaged Damage which reduces the flow of the exhaust gas will create increased back pressure in the engine Reduction in exhaust flow can result from crushed muffler outlets or melted catalyst brick inside the converter It may be necessary to measure the back pressure in the ex haust system To determine if the back pressure in the engine is correct use the following procedure Diagnostic Aids Tools Required e J 35314 A Diagnostic Scan Tool e IMPCO Fuel System diagnostic tool Check at Heated Exhaust Gas Oxygen Sensor HEGO Carefully remove the HEGO 2 Install exhaust backpressure test J35314 a in place of the HEGO See Illustration 3 With the engine idling at normal operating temperature observe the exhaust system back pressure reading on the gage Reading should not exceed 8 6 kPa 1 25 psi 4 Increase engine speed to 2000 RPM and observe gage Reading should not exceed 20 7 kPa 3 psi 5 Ifthe back pressure at either speed exceeds specifica tion a restricted exhaust system is indicated 4 3 liter Emission Certified GM Engine 6 Inspect the entire exhaust system for a collapsed pipe heat distress or possible internal muffler failure Ifthere are no obvious reason
63. poor idle quality IMPCO Technologies Engine Service Manual 13 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Engine Mechanical Check Check the engine for the following Broken motor mounts Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes 14 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Surges Chuggles DEFINITION The engine has a power variation under a steady throttle or cruise The vehicle feels as if it speeds up and slows down with no change in the accelerator pedal Preliminary Checks e Refer to Important Preliminary Checks Be sure the driver understands the Torque Converter Clutch operation Sensor Checks Check the Heated Exhaust Gas Oxygen Sensor HEGO performance Fuel System Checks Ignition System Checks Additional Check Check for Rich or Lean symptom that causes the condition Drive the vehicle at the speed of the complaint Monitoring the oxygen sensors will help identify the problem Check the fuel pressure while the condition exists Refer to LPG Fuel System Diagnosis Verify proper fuel control solenoid operation that LPG manual shut off valve is fully open Check the in line fuel filter for restrictions Check for the proper ignition output voltage using the spark tester J26792 or the equivalent Verify that the sp
64. possible fuel problem 6 If conditions were not corrected a worn cam worn intake or exhaust valves or other engine mechanical failures may be at fault DTC P0171 or P0174 Did you perform the Diagnostic System Check Engine 1 Controls Go to Step 2 2002 MIL Van August 7 2001 IMPCO Technologies Engine Service Manual Yes Go to Diagnostic System Check Engine Controls 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0171 or P0174 cont d Important If any DTCs are set other than 171 P0174 refer to those DTCs before continuing 1 Install the scan tool 2 Start and idle the engine at the normal operating temperature in Closed Loop Record the Long Term Fuel Trim Turn OFF the engine Turn ON ignition with engine OFF Review the Freeze Frame Records and or Failure Records and record displayed data for this DTC Does the scan tool indicate that the Long Term Fuel Trim is greater than the specified value 1 Operate engine at idle 2 Using the scan tool observe HO2S parameters Does the scan tool indicate that the parameter is within the specified range and fluctuating Turn OFF the engine Visually and physically inspect the following items Vacuum hoses for splits kinks and proper connections Refer to Emission Hose Routing Diagram Ensure that the vehicle has sufficient fuel in tank If fuel pressure is too low this DTC may set Refer to Fuel
65. problems found Refer to Wiring Repairs in Engine IMPCO Technologies Engine Service Manual 15 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine emove all test equipment except the DSI ystem OK Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 111 check for any stored codes Does the engine operate normally with no stored codes 16 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 17 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 111 IAT High Voltage Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition IAT Sensor Voltage greater than 4 95 MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other se
66. property damage Less severe than WARNING but has the potential to cause injury or dam age Also used to notify of situations that could lead to eventual failure injury or damage IMPORTANT Denotes situations which could influence safety or proper performance of the vehicle or compo nent NOTICE Significant item of information To reduce the chance of personal injury and or property dam age the following instructions must be carefully observed 2 IMPCO Technologies Engine Service Manual Proper service and repair are important to the safety of the service technician and the safe reli able operation of all engines The service pro cedures recommended and described in this ser vice manual are effective methods of performing service and repair Some of these procedures require the use of tools specially designed for the purpose If part replacement is necessary the replacement part must be of the same part number or equiva lent part Do not use a replacement part of lesser quality In the case of replacement parts for the emission control system use only genuine OEM replacement parts Before using a replacement part service proce dure or a tool which is not recommended by the engine manufacturer it must first be determined that neither personal safety nor the safe opera tion of the engine will be jeopardized by the replacement part service procedure or the tool selected Special service t
67. replacement complete 74 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 Remove all test eguipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 135 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 75 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 142 Crank Sync Noise ECM 5 volts Crank Sensor Crank Conditions for setting the DTC Crankshaft Position sensor Check Condition Engine running Fault Condition 1 invalid crank re sync MIL On during active fault and for 10 seconds after active fault Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Circuit Description The Crankshaft Position sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft It determines crankshaft position by monitoring the pulse wheel The Crankshaft Position sensor is used to measure engine RPM and its signal is used to synchronize the ignition and fuel sy
68. sensor wire harness connector circuit as Disconnect ECM wire harness connector necessary Refer to Key ON mE x Wiring Repairs Using a high impedance DVOM check for continuity in Engine between HO2S connector signal pin B and engine Electrical ground Do you have voltage e Using a high impedance DVOM check for continuity Repair the Go to Step 7 HO2S signal necessary e Do you have continuity Refer to in Engine Electrical DTC 241 Adaptive Lean Fault High Limit nn Are any other DTCs present with this chart Key ON Engine running Battery Go to Step 5 Repair the Back probe the HO2S sensor connector heater voltage circuit as terminals for negative and for positive necessary Using a DVOM check for voltage Refer to Wiring Repairs Do you have voltage in Engine Electrical between HO2S connector sensor ground pin A and circuit as Wiring Repairs IMPCO Technologies Engine Service Manual 105 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 241 check for any stored codes Do
69. that sensor may be a default limp home value and the voltage value will be the actual sensor voltage Use the voltage value when performing diagnostics unless directed to do otherwise by the diagnostic trouble tree 6 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 Graphing and Data Logging EDIS ECI Serial Communications E 1 xi Ele Page Flash CommPort PlotjLog Hel a Link error attempting reconnect Toggle Page F9 Gauges EControls Inc Connected at 19200 bps Conti and stna packe o ToggeTesCel F10 Ford Power Products ECM interface MiL _ Coolant Temperature Intake Air Temperature S JES Manifold Pressure 250 250 Engine Speed re 75 200 200 Selpoint 1000 rpm 50 100 0 Max Governor Setpoint 4500 rem 29 1 50 Pulse width 362 ms 00 150 0 EGOI 0095 volts a EGO2 0452 vols 43 psia 8 degF m el x Minimum Y Value 21000 Sampling Interval ms F 15 00 T Single Shot Acquisition Foot Pedal Position Close Pe Maximum Y Value 4000 00 Time Ine valls 2710 00 100 2_ amp 0 40 4000 20 0 0x 3200 2400 amp 1600 800 07 1 26 28 30 3 36 time s Graphing the values and voltages can be a very useful tool in doing intermittent diagnosis The system diagnostic monitoring software includes graphing and data loggin
70. the DTC Memory 1 Disconnect the TMAP sensor 2 Idle the engine until the Malfunction Indicator Lamp illuminates The ECU should store a TMAP DTC The TMAP DTC should remain in the memory when the ignition is turned OFF If the TMAP DTC does not store and remain the ECM is faulty Additional Checks IMPCO Technologies Engine Service Manual 3 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine No Start DEFINITION The engine cranks OK but does not start Preliminary Checks e Refer to Important Preliminary Checks Control Module Checks e scan tool is available e Check for proper communication with both the ECM Check the 3A inline fuse in the ECM battery power circuit Refer to Engine Controls Schematics Check battery power ignition power and ground circuits to the ECM Refer to Engine Control Schematics Verify voltage and or continuity for each circuit Sensor Checks Check the TMAP sensor Check the Magnetic pickup sensor RPM Fuel System Checks Important A closed LPG manual fuel shut off valve will create a no start condition Check for air intake system leakage between the mixer and the throttle body Verify proper operation of the low pressure lock off solenoids Verify proper operation of the fuel control solenoids Check the fuel system pressures Refer to the LPG Fuel System Diagnosis Check for proper mixer air valve operation Ignition System Checks Note LPG being a gase
71. the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability IMPCO Technologies Engine Service Manual 65 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 134 BP High Pressure Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Barometric Pressure Check Condition Key On Fault Condition BP greater than 16 psia MIL On for active fault and for 2 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The BP Barometric Pressure is estimated from the TMAP sensor The barometric pressure value is used for fuel and airflow calculations This fault sets in the event the BP value is out of the normal range 66 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 134 BP High Pressure Motorola TMAP step metom Ye Ne Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to step 3 Intermittent problem DST Diagnostic Scan Tool connected in Go to Intermittent System Data Mode section Does DST display MAP pressure of 16 psia or Remove all test equipment except the DST System Ok Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the igni
72. this Section NOTICE Before attaching field lead be sure solenoid terminal is secure by tightening nut next cap this nut is not tight the cap may be damaged during installation of the field lead and cause starter to fail later Tighten Nut on solenoid field terminal to 8 71 Ib in 11 Solenoid 12 Field lead to solenoid terminal Tighten e Attaching nut to 8 71 Ib in IMPCO Technologies Engine Service Manual SECTION 1 7 IGNITION SYSTEM IMPCO Technologies Engine Service Manual 1 1C7 Ignition System 4 3 liter Emission Certified GM Engine IGNITION SYSTEM SPECIFICATIONS U wee Eis IT 1000 chmsperm RATA AC _ FASTENER TIGHTENING SPECIFICATIONS Ignition Coil Mounting Screws Ignition Module Mounting Screws J 26792 Spark Tester J 35616 A Connector Test Adapter Kit 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 Heated Oxygen Sensors sio ip 765593 430019 Legend 1 Heated Oxygen Sensor HO2S Bank 1 3 Heated Oxygen Sensor HO2S Bank 2 Sensor 2 Sensor 1 2 Heated Oxygen Sensor HO2S Bank 1 Sensor 1 IMPCO Technologies Engine Service Manual 3 209622 Legend 1 Vehicle Speed Sensor VSS 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition Syst
73. to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 531 check for any stored codes Does the engine operate normally with no stored codes 134 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 135 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 532 External 5 V Ref Higher Than Expected LTGRN R 5 Volts ECM Conditions for Setting the DTC External 5V reference Check Condition Cranking with battery voltage greater than 8 volts or engine running Fault Condition 5V reference voltage higher than 5 4 volts MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Circuit Description The External 5 Volt supply powers some of the sensors and other components in the system The accuracy of the 5 Volt supply is very important to the accuracy of the sensors and therefore control by the ECM The ECM to determine if they are overloaded shorted or otherwise out of specification monitors the 5 Volt supply This fault will set if the 5 Volt reference is above 5 4 volts 136 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 532 Exter
74. tool Fuel Trim Reset function in order to reset the Long Term Fuel 1 Use a scan tool in order to clear the DTCs Turn OFF the ignition for 30 seconds Start the engine Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and then pass Go to Step 8 Go to Step2 Use a scan tool in order to observe the stored information in Capture Info Does the scan tool display any DTCs that you have not diagnosed Go to Diagnostic Trouble Code DTC List System OK 10 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0172 or P0175 SIE ID 693637 Circuit Description The powertrain control module PCM controls the air fuel metering system in order to provide the best possible combination of driveability fuel economy and emission control Fuel delivery is controlled differently during open and closed loop During open loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input During closed loop the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments If the oxygen sensors indicate a lean condition fuel trim values will be above 0 percent If the oxygen sensors indicate a rich condition fuel trim values will be below percent Short Term fuel trim values change rapidly in response to the heated oxyge
75. use Teflon tape on the pipe fittings use only a liquid pipe sealant 6 Install the filter to the retaining device and secure Install the outlet fuel line and tighten to specification Tighten 27 Nm 20 ft Ibs 8 Reconnect the negative battery cable 9 Open manual shut off valve 10 Start the vehicle and leak check the propane fuel system at each serviced fitting Refer to Propane Fuel System Leak Test 4 3 liter Emission Certified GM Engine Fuel System 1E1 Elbow Fitting 40 ___ Inlet Fitting to Lock off Fitting Retaining Pins x a x x Electric Lock Off FTVRetalningBolts N x X ET EN Water Fitting gt Secondary Test Port Cap x gt Low Pressure Regulator Qr u lt 7 Water Fitting Vapor Outlet Fitting PTV FIGURE 2 LOW PRESSURE REGULATOR AND LOCK OFF ASSEMBLY LOW PRESSURE LOCK OFF LPL tion REPLACEMENT 3 Install the fuel inlet line Figure 2 4 nm the fuel line fitting to the LPL Tighten Removal Procedure 27 Nm 20 ft Ibs 1 Relieve the propane fuel system pressure Refer to Propane Fuel System Pressure Relief Connect the LPL electrical connector 2 Disconnect the negative battery cable Connect the negative battery cable Disconnect the LPL electrical connector Open the tank manual shut off valve 4 Disconnect the LPG fuel inlet line from the LPL inlet Start the vehicle and leak check the propane fuel system fitting at each serviced fitting
76. vehicle at the speed of the complaint Monitoring the oxygen sensors will help identify the problem Check for a sticking mixer air valve Verify proper operation of the PTV and FTV Perform a cylinder compression test Refer to Engine Mechanical in the Service Manual Check the LPR fuel pressure Refer to the LPG Fuel System Diagnosis Check mixer module assembly for proper installation and connection Ignition System Checks Check for the proper ignition output voltage using the spark tester J26792 or the equivalent Verify that the spark plugs are correct for use with LPG RA2LTS Check the spark plugs Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Blistered insulators Heavy deposits e Check the spark plug wires by connecting an ohmmeter to the ends of each wire in question If the meter reads over 30 000 ohms replace the wires Additional Checks Important The LPG Fuel system works on a fumigation principle of fuel introduction and is more sensitive to intake manifold leakage than the gasoline fuel supply system Check for vacuum leaks Vacuum leaks can cause a higher than normal idle and low throttle angle control command Check the ECU grounds for being clean tight and in their proper locations Check the battery cables and ground straps They should be clean and secure Erratic voltage may cause all sensor readings to be skewed resulting in
77. wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 131 check for any stored codes Does the engine operate normally with no stored codes 50 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 51 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 131 MAP High Pressure Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Manifold Absolute Pressure Check Condition RPM greater than 800 Throttle Command less than 10 steady MAP and TPS Fault Condition MAP greater than 18 psia TPS less than 10 and engine RPM greater than 1800 MIL On for remainder of key on cycle Adaptive Disabled for remainder of key on cycle Closed Loop Enabled and allowed to stay at limit Misc Fueling is based on RPM and TPS Limp Home Condition during this fault Circuit Description The TMAP is a combined inlet manifold temperature and pressure sensor connected to the intake manifold It is used to measure the pressure of air in the manifold prior to induction into the engine The pressure reading is used in conjunction with other inputs to determine the airflow rate to the engine which also determines the fuel flow rate This fault will set when the MAP reading is higher than it should be for the given TPS and RPM When the fa
78. 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 134 BP High Pressure Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Barometric Pressure Check Condition Key On Fault Condition BP greater than 16 psia MIL On for active fault and for 2 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The BP Barometric Pressure is estimated from the TMAP sensor The barometric pressure value is used for fuel and airflow calculations This fault sets in the event the BP value is out of the normal range 64 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 134 BP High Pressure _ letom Vaw Yes No Did you perform the On Board OBD System Check Go to 2 Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent DST Diagnostic Scan Tool connected in section System Data Mode Does DST display MAP pressure of 16 psia or System Ok Go to OBD System Check After operating the engine within the test parameters of DTC 134 check for any stored codes Does the engine operate normally with no stored codes Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start
79. 25 cont d No Use a scan tool in order to observe the stored information Go to Diagnostic Capture Info Trouble Does the scan tool display any DTCs that you have not diagnosed Code DTC List System C 22 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 194429 Circuit Description The knock sensor KS produces an AC voltage at all engine speeds and loads The powertrain control module PCM adjusts the spark timing based on the amplitude and frequency of the KS signal The PCM uses the KS signal in order to calculate the average voltage The PCM assigns a voltage value The PCM checks the KS and the related wiring by comparing the actual KS to the assigned voltage range A normal KS signal should stay within the assigned voltage range This DTC will set if the KS signal is outside the assigned voltage range or if the signal is not present Conditions for Running the DTC e DTCs P0116 P0117 P0118 P0121 P0122 P0123 P0125 P1114 P1115 P1121 P1122 are not set The engine coolant temperature ECT is more than 60 140 F The engine run time is more than 10 seconds The manifold absolute pressure MAP is less than 44 kPa The engine speed is between 2 000 3 000 RPM The system voltage is more than 10 volts Conditions for Setting the DTC The KS is outside the assigned range or not present SIO ID 727820 Actio
80. 262 System Voltage High Value s Yes No Did you perform the On Board OBD System Check Go to ET 2 Go to OBD System Check Section Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine greater than 1500 rpm Does DST display system voltage less than 18 volts Check voltage at battery terminals with DVOM with engine speed greater than 1500 rpm Is it greater than 18 volts Repair the charging system Has the charging system been repaired Replace ECM the replacement complete Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 262 check for any stored codes Does the engine operate normally with no stored codes Intermittent Go to Step 3 problem Go to Engine Electrical Intermittent section Go to Step 4 Go to Step 5 Go to Step 6 System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 119 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 511 COP Failure ECM Microprocessor Conditions for Setting the DTC Engine Control Module Check Conditi
81. 4 3 liter Emission Certified GM Engine General Information OA SECTION 0A GENERAL INFORMATION IMPCO Technologies Engine Service Manual 1 OA General Information 4 3 liter Emission Certified GM Engine FUEL SYSTEMS CAUTIONS CAUTION Do not smoke carry lighted tobacco or use a lighted flame of any type when working on or near any fuel related component Highly flammable air fuel mixtures may be present and can be ignited causing personal injury CAUTION Do not allow propane to contact the skin Propane is stored in the fuel tank as a liquid When propane contacts the atmosphere it immedi ately expands into a gas resulting in refrigeration that can cause severe burns CAUTION Do not allow propane to accumulate in areas below ground level such as in a service pit or underground ventilation systems Propane is heavier than air and can displace oxygen creating a dangerous condition It is important to note that this manual contains various Warnings Cautions and Notes that must be carefully ob served in order to reduce the risk of personal injury during service or repair Improper service or repair may damage the engine or render it unsafe or fail to make the engine emis sions compliant It is also important to warn of all hazardous consequences that might result from careless treatment of the engine Failure to observe these items could influence terms ofthe warranty Failure to heed could result in death injury or
82. 4 Go to Step 10 Inspect for poor connections at the fuel pump relay Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 12 Inspect for poor connections at the harness connectors of the PCM Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 13 Repair the ground circuit of the relay Refer to Wiring Repairs in Wiring Systems Did you complete the repair Go to Step 14 Replace the fuel pump relay Did you complete the replacement Go to Step 14 Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement Go to Step 14 1 Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass Go to Step 15 Go to Step2 With a scan tool observe the stored information Capture Info Go to Diagnostic Does the scan tool display any DTCs that you have not diagnosed Trouble any 9 Code DTC List System OK 16 IMPCO Technologies Engine Service Manual n Description vertrain control module PCM uses information crankshaft position CKP sensor and the ft position CMP sensor in order to determine a engine
83. 9 Armature and Drive Assembly Current draw readings that are over specifi cations indicate shorted turns or a ground in the solenoid windings Replace the starter inanan CES ao m oo u 4 55 1C5 Starter THRUST COLLAR 4 3 liter Emission Certified GM Engine Current draw readings that are under speci fications indicate excessive resistance A zero indicates an open Check repair replace starter solenoid are serviced as an assembly STARTER MOTOR ASSEMBLY Figures 4 16 4 19 through 4 21 Assemble 1 Lubricate inner gear teeth and bearing Figure 4 20 Installing Retainer Washer and Ring solenoid RECESS BEARING 0 25 mm 0 01 in INTO CASTING Figure 4 21 Drive End Housing Bearing 6 IMPCO Technologies Engine Service Manual planetary gears and armature shaft gear teeth lightly with lubricant Refer to figure 4 19 Inner gear and drive over armature shaft with pinion away from armature Pinion stop collar onto armature shaft New pinion stop retainer ring into groove on shaft Do not reuse old ring Thrust collar to end of shaft with small flange toward retainer ring Use pliers as shown in figure 4 20 to snap pinion stop collar over retainer ring 4 3 liter Emission Certified GM Engine Inspect Drive end housing bearing and armature commu tator end bearing When dry the armature commu tater end bearing
84. AGNOSE THE SPECTRUM SYSTEM A laptop computer is the preferred tool for performing diagnostic testing of the Spectrum system A laptop computer with the system diagnostic cable and diagnostic software is used to read and clear Diagnostic Trouble codes It is also used to monitor sensor and actuator values The diagnostic software also performs several special tests The following procedures will assist you in using a laptop computer to diagnose the Spectrum system INSTALLING THE SPECTRUM DIAGNOSTIC SOFTWARE Loading Software and Connecting the Computer Start Windows Insert the Diagnostic Interface software CD Click on the START button From the Start menu select RUN In the command line text box type the letter of your CD ROM drive followed by setup for example e setup then click OK Follow the on screen instructions Connecting a Laptop Computer to the Spectrum System Connect the system diagnostic cable to the 5232 port on the back of the computer If you do not have RS 232 port use the USB to RS232 adapter cable Connect diagnostic cable to the diagnostic connector on the engine harness The diagnostic connector is a square 4 pin connector located near the Spectrum system ECM Turn the computer ON Start Windows From the Start menu select Programs Select IMPCO Display Place the ignition key in the ON position The system Gauge screen should n
85. CTION AND armature is shorted Clean between the commutator bars and recheck armature TESTIN G for short circuits If saw blade still vibrates Figures 4 17 and 4 18 replace the armature Inspect Using a self powered test lamp place one 1 Clean all starting motor parts but DO NOT lead on the commutator and the other lead USE GREASE DISSOLVING SOLVENTS FOR CLEANING THE OVERRUNNING CLUTCH OR ARMATURE because solvents dissolve the grease packed in the clutch and damage armature insulation Test drive assembly action The pinion should turn freely in the overrunning direction Check pinion teeth to see that they have not been chipped cracked or excessively worn Replace assembly when necessary Badly chipped pinion teeth can indicate chipped ring gear teeth which should be replaced when necessary The roll type drive assembly acquires no lubrication however the drive assem bly should be wiped clean Do not clean in degreasing tank or with grease dissolving solvents this dissolves the lubricant in the drive mechanism Armature commutator When commutator is dirty clean with 400 grit polishing cloth When commutator is rough the armature should be replaced Do not undercut or turn commuta tors Inspect the points where the armature conductors join the commutator bars to make sure they have a good connection A burned commutator bar is usually evidence of a poor connection Brushes and brush holders Wh
86. Closed Loop Disabled during active fault Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the Adaptive multiplier This fault will set if HO2S is cold non responsive or inactive for 120 seconds or longer 94 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine DTC 212 HO2S Open Inactive on Did you perform the On Board OBD System Check Go to mm 2 Go to Step 5 Go to step 4 Go to step 7 Go to Step 6 Go to Step 8 Key ON Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine to full operating temperature and then idle for a minimum of 2 minutes Does DST display HO2S voltage fixed between 0 4 and 0 5 volts after 2 minutes of idle run time e Back probe HO2S wire harness connector and check for voltage between HO2S connector heater ground pin D and battery voltage positive Do you have power e Back probe HO2S wire harness connector and check for voltage between HO2S connector heater power pin C and engine ground Do you have power Key OFF Disconnect HO2S connector and ECM connector Key ON Check for continuity between HO2S sensor connector ground pin A and ECM HO2S sensor ground PIN 49 Do you have continuity between them
87. DTC Engine Coolant Temperature Check Condition Engine Running Fault Condition ECT sensor voltage less than 0 05 MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Circuit Description The ECT Engine Coolant Temperature sensor is a temperature sensitive resistor located in the engine coolant It is used for the engine airflow calculation gasoline cold enrichment and to enable other temperature dependant features The ECM provides a voltage divider circuit so that when the coolant is cool the signal reads higher voltage and lower when warm This fault will set if the signal voltage 15 less than 0 05 volts anytime the engine is running The ECM will use a default value for the ECT sensor in the event of this fault 42 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 122 ECT VOLTAGE LOW Value s Yes mo Did you perform the On Board OBD System Check ooo Go to OBD System Check Section Go to step 3 Intermittent e KeyOn problem DST Diagnostic Scan Tool connected in Go to e System Data Mode Does DST display ECT voltage of 0 05 or less Key Off Go to step 4 Go to step 5 e Disconnect the ECT wire harness connector e Key ON Does the DST display ECT voltage of 4 9 volts or greater 4 Replace ECT sensor Go to Step 8 Is the replacement
88. Engine Service Manual as necessary Refer to Wiring Electrical as necessary Refer to Wiring Electrical Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Go to Intermittent Go to step 5 Repair the circuit Repairs in Engine Repair the circuit Repairs in Engine 61 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine e Probe MAP signal circuit with a test light Go to Step 9 Go to step 13 connected to battery voltage Does the DST display MAP voltage of 4 0 or greater Go to step 10 Repair the circuit Disconnect ECM connector as necessary Check for continuity between TMAP sensor Refer to Wiring connector and ECM 5 volt reference signal Repairs in Engine m Electrical Do you have continuity between them Check for continuity between TMAP sensor Repair the circuit Go to Step 11 connector 5 volt reference pin C signal and engine as necessary ground Refer to Wiring Do you have continuity Repairs in Engine Electrical Inspect ECM connector and wire harness Repair the circuit Go to Step 16 connector terminals for corrosion contamination as necessary or mechanical damage Refer to Wiring Any problems found Repairs in Engine Electrical Replace ECM Refer to ECM replacement in the Go to step 17 Engine Controls Section Is the replacement complete Disconnect ECM connector Go to Step 14 Repair the circuit Check for continuity
89. Engine Service Manual 123 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 513 A D Loss Microprocessor Conditions for Setting the DTC Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM has checks that must be verified each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 124 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 513 A D Loss Yes mo 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code rauen Does D
90. GASOLINE MPFI FUEL SYSTEM PRESSURE RELIEF THE FUEL SYSTEM OPERATES AT PRES SURES UP TO 135 KPA 20PSI TO MINI MIZE THE RISK OF FIRE AND PERSONAL INJURY RELIEVE THE GASOLINE FUEL SYSTEM PRESSURE WHERE APPLICA BLE BEFORE SERVICING THE PROPANE FUEL SYSTEM COMPONENTS To relieve Gasoline fuel system pressure Disconnect the electrical connector at the fuel pump Start and run the vehicle until the engine stalls Turn the ignition switch OFF Remove the Cap on the gasoline pressure test port na Wrap a shop towel around the fitting and using a small screw driver depress valve and insure there is no pres sure left in the system IMPORTANT e Residual vapor pressure will be present in the fuel system Ensure the work area is well ventilated be fore disconnecting any fuel line IMPCO Technologies Engine Service Manual 9 1E1 Fuel System GASOLINE FUEL SYSTEM LEAK TEST NEVER USE AN OPEN FLAME OF ANY TYPE TO CHECK FOR PROPANE FUEL SYSTEM LEAKS Always inspect the gasoline fuel system for leaks after per forming service Check for leaks at the fittings of the serviced or replaced component 4 3 liter Emission Certified GM Engine FIGURE 7 INJECTOR RAIL AND MANIFOLD FUEL RAIL REPLACEMENT Figure 7 1 Disconnect the negative battery cable 2 Disconnect the air duct FIGURE 6 THROTTLE POSITION SENSOR 3 Remove the throttle body assembly Refer to Throttle Body Assembly Replacement THROTT
91. Go to Step 2 Go to Diagnostic System Check Engine Controls System OK Inspect for the following Check for excessive fuel in the crankcase Inspect the Evaporative Emissions Control System Test fuel pressure regulator for proper operation Refer to Fuel System Diagnosis Check to ensure that all injectors are functioning G S properly Refer to Fuel Injector Coil Test o ii E gt NE Perform the Fuel Injector Balance Test Refer to Fuel He al in Injector Balance Test with Special Tool Engine Did you find and correct the condition Go to Step 7 Mechanical 4 3L 12 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0200 SIE ID 789930 Circuit Description The powertrain control module PCM enables the appropriate fuel injector on the intake stroke for each cylinder An ignition voltage is supplied to the fuel injectors The PCM controls each fuel injector by grounding the control circuit via a solid state device called a driver The PCM monitors the status of each driver If the PCM detects an incorrect voltage for the commanded state of the driver a fuel injector control diagnostic trouble code DTC sets Conditions for Running the DTC The engine is running The ignition voltage is between 6 18 volts Conditions for Setting the DTC The PCM detects an incorrect voltage on the fuel injector control circuit The condition exists for 5 se
92. HO2S sensor Is the replacement complete Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 211 check for any stored codes Does the engine operate normally with no stored codes Step ves No Did you perform the On Board OBD System Check Go to 2 Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent section Repair the Go to Step 4 circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the Go to Step 5 circuit as necessary Refer to Wiring Repairs in Engine Electrical System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 93 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 212 HO2S Open lnactive Sensor Sensor Ground To System Power Relay To Engine Ground Conditions for Setting the DTC Heated Oxygen Sensor Check condition Engine running Fault condition HO2S cold persistently more than 120 seconds MIL On during active fault and for 1 second after active fault Adaptive Disabled during active fault
93. IL on the second consecutive ignition cycle that the diagnostic runs and fails The control module records the operating conditions at the time the diagnostic fails The first time the diagnostic fails the control module stores this information in the Failure Records If the diagnostic reports a failure on the second consecutive ignition cycle the control module records the operating conditions at the time of the failure The control module writes the operating conditions to the Freeze Frame and updates the Failure Records SIO ID 727824 Conditions for Clearing the MIL DTC The control module turns OFF the malfunction indicator lamp MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail A current DTC Last Test Failed clears when the diagnostic runs and passes A history DTC clears after 40 consecutive warm up cycles if no failures are reported by this or any other emission related diagnostic Clear the MIL and the DTC with a scan tool Diagnostic Aids The system will go lean if an injector is not suppling enough fuel A lean condition could be present during high fuel demand Using scan tool review Failure Records If an intermittent condition is suspected refer to Intermittent Conditions Test Description The numbers below refer to the step numbers on the diagnostic table 5 If conditions were not corrected refer to Fuel System Diagnostics for a
94. LE POSITION SENSOR 4 Disconnect the fuel supply line to the rail as sembly REPLACEMENT 5 Disconnect the fuel return line to the rail assembly 6 Disconnect the vacuum line to the Pressure regulator Figure 6 nn 7 Remove the four 4 fuel rail retaining bolts to the mani 1 Disconnect the TPS electrical connect fold and retain 2 Remove and retain the two 2 screws 8 With a screw driver press back on the six 6 injector 3 Remove the TPS shaft seal retaining clips and retain 4 Remove the TPS 9 Carefully lift the fuel rail off the injectors Installation Procedure Install the TPS shaft seal With the throttle valve closed install the TPS Rotate counterclockwise until mounting holes align Mao Un Install two 2 screws and tighten to specification Tighten 2 Nem 18 Ib in 10 IMPCO Technologies Engine Service Manual Installation Procedure IMPORTANT Lightly Lubricate the o ring of the throttle body as sembly and the inlet o ring on each injector Cover Throttle body adapter opening and injectors to prevent debris from entering engine or the injec tors until reassembly 4 3 liter Emission Certified GM Engine 10 Carefully place the fuel rail over all the injector and press down to set the rails ll Install the six 6 injector retaining clips 12 Secure the fuel rail to the manifold with the four 4 re taining bolts Tighten 12 Nem 106 Ib in 13 Connect the vacuum line to the pressure regulator 14 C
95. M Engine 5 bly to mixer Remove and discard the mixer to throttle body assem bly o ring Installation Procedure IMPORTANT Lightly Lubricate the o ring of the Mixer to throttle body assembly o ring before installing Cover Throttle body adapter opening to prevent de bris from entering engine until reassembly Install Mixer to throttle body assembly o ring onto the mixer Install the mixer to the throttle body assembly and se with the 4 retaining screw Tighten 9 Nem 80 Ib in Install Throttle body Refer to Electronic Throttle Control Device Replacement FIGURE 5 THROTTLE POSITION SENSOR Fuel System 1E1 THROTTLE POSITION SENSOR REPLACEMENT Figure 5 1 Disconnect the TPS electrical connect 2 Remove and retain the two 2 screws 3 Remove the TPS shaft seal 4 Remove the TPS Installation Procedure 99 1 9 ta Install the TPS shaft seal With the throttle valve closed install the TPS Rotate counterclockwise until mounting holes align Install two 2 screws and tighten to specification Tighten 2 Nem 18 Ib in COOLANT HOSE REPLACEMENT Drain coolant Using a hose clamp pliers disconnect both hose clamps on each hose Remove the coolant inlet hose form each fitting Remove the coolant outlet hose Installation Procedure IMPORTANT ou fF WN Coolant hose are specifically designed DO NOT use hose material or length other than the OEM specified parts DO NOT mix the inlet
96. MAP IMPCO Technologies Engine Service Manual 27 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 28 DTC 113 IAT Higher Than Expected 1 Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition Intake Air Temperature greater than 210 degrees F and engine RPM greater than 1000 MIL Will flash at 2 Hz twice per second during active fault Adaptive Disabled during active fault Closed Loop Enabled Power Derate Level 1 Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The IAT is a calculated value based mainly on the IAT sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow This fault will set if the Intake Air Temperature is greater than 210 degrees F and engine RPM is greater than 1000 and Power Derate 1 will be enforced During this fault maximum throttle position is 50 and the MIL light will flash twice per second Di
97. Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 INJECTOR TEST EDIS ECI Serial Communications 181 File Page Flash Comm Port Plot Log Help Link error attempting reconnect al Toggle Page F9 o Faults Inc Connected at 19200 bps lar Conto and instremmentstion Spaciatste Toggle Test F10 MIL Et Sysem Bew yareaee Col una Number Engine Speed 1000 mm Run Mode Running TPS command gg 25 firing order dwellms fring order voltage voltage Manifold Pressure 435 psia Fuel Type Gasoline TPS position 35 1 425 1 0 3 142 Coolant Temperature 107 3 degF FuelContolMode CLActive FPP command 00 Z 2 425 2 01 141 Cylinder Head Temp 107 3 degF Govemor switch state Gova FPP position 00 z oo osf 10 Manifold Temperature 788 degF Active govemor type Mn TPS1 voltage 0 685 volts 4 02 144 Intake Air Temperature 79 3 degF Active governor mode Droop TPS2 voltage 4275 vols 5 oof oo 138 Brake inputlevel Open FPPI voltage 0448 vols B oof 00 Viw 136 vots Gerne pne j FPP2 voltage 0000 vols Hour meter 12642 hous IVS voltage 5000 vols Cumulative starts 39 starts Glosed Loop Digla input Vohages Diagnostic Modes EGOI 0503 vots Fuel select voltage 102 vols il Normal w Closed oop 1 45 Fuel pump voltage 137 vols il Normal Adaptive 1 Imm zi Gov voltage 206 vol
98. NG Weather Pack A Weather Pack connector can be identified by a rubber seal at the rear of the connector This connector which is used in the engine compartment protects against moisture and dirt which could create oxidation and deposits on the terminals This protection is important because of the very low voltage and current levels found in the electronic system 1 OPEN SECONDARY LOCK HINGE ON CONNECTOR FEMALE MALE CONNECTOR CONNECTOR VE J SECONDARY LOCK HINGE 2 REMOVE TERMINAL USING TOOL amp PUSH TO RELEASE TERMINAL TOOL J 28742 BT8234 A 3 CUT WIRE IMMEDIATELY BEHIND CABLE SEAL en 4 REPLACE TERMINAL A SLIP NEW SEAL ONTO WIRE B STRIP 5 mm 2 OF INSULATION FROM WIRE C CRIMP TERMINAL OVER WIRE AND SEAL 5 PUSH TERMINAL AND CONNECTOR AND ENGAGE LOCKING TANGS 6 CLOSE SECONDARY LOCK HINGE WIRE FIGURE 3 WEATHER PACK TERMINAL REPAIR 1 I pa L 3 35689 OR BT 8446 4 CONNECTOR BODY 5 SEAL FIGURE 2 METR PACK SERIES 150 TERMINAL REMOVAL IMPCO Technologies Engine Service Manual 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi Repair of a Weather Pack terminal is shown in Figure 3 23 Use tool J M28742 or BT8234 A to remove the pin and sleeve terminals If removal is attempted with an ordinary pick there is a good chance that the terminal will be bent or deformed Unlike standard blade type terminals th
99. NotUsed 34 IMPCO Technologies Engine Service Manual INSTRUMENT PANEL CONNECTOR C023 Wire Color Function IMPCO Technologies Engine Service Manual 35 INSTRUMENT PANEL CONNECTOR C024 Black White Aux In PD2 ___ Yellow Dk Blue Aux In PU2 Dk Blue Yellow Aux In PU1 ID Pink Yellow Fuel Pump Pink Dk Green Relay Fused Power 36 IMPCO Technologies Engine Service Manual FUEL TRIM VALVE CONNECTOR C025 ey gt Red White Injector 7 B Orange Lt Blue IMPCO Technologies Engine Service Manual 37 FUEL LOCKOFF CONNECTOR C026 White Black Fuel Lockoff B VW 38 IMPCO Technologies Engine Service Manual PRESSURE TRIM VALVE CONNECTOR C027 White Red B gt gt Orange Lt Blue IMPCO Technologies Engine Service Manual 39 INJECTOR 1 CONNECTOR C028 Orange Lt Blue Fuel Trim Valve IB Brown Lt Blue Injector 1 40 IMPCO Technologies Engine Service Manual INJECTOR 2 CONNECTOR C029 ac Orange Lt Blue Fuel Trim Valve Tan Lt Blue Injector 2 IMPCO Technologies Engine Service Manual 41 INJECTOR 3 CONNECTOR C030 ac Orange Lt Blue Fuel Trim Valve IB Brown Orange Injector 42 IMPCO Technologies Engine Service Manual INJECTOR 4 CONNECTOR C031 Orange Lt Blue Fuel Trim Valve Brown
100. Off a gj Overspeed voltage 50 vols ME nabo ee SnapShot SnapShot ClosedHoop 2 ox i ase Base Custom Mn m Dil pressure voltage 00 vols Definitions Definitions Definitions em ______ EMPTY IMAP tmr sec JEMPTV Historic Faults Active Faults _ EMPTY TP pat EMPTY emi leme EM CL_BM1 EMPTY A A A BM2 A BM2 Vbat Flight Data pet Custom ITPS pet Definitions Oi vods ___ EMPTY EGO2 volts EMPTY Pr o TRIM DC HM hours To select this test mode the engine must be off but the key must be in the ON position The DBW Drive By Wire test mode allows the technician to control the throttle directly with the foot pedal or throttle input and is used during the diagnostic routines specified for FPP and TPS for Spectrum systems that use DBW FPP position displays the current position of the foot pedal as a percentage FPP volts display the voltage which the ECM is reading from the FPP sensor TPS Command displays the commanded throttle position expressed as a percentage which is being sent to the throttle TPS Position is the actual percent of throttle opening being sent to the ECM from the throttle TPS volts display the actual TPS signal voltage the ECM is receiving from the throttle Using a Diagnostic Jumper to Diagnose the ECI System If you do not have access to a laptop computer it is still possible to access the Di
101. P sensor Check for proper operation ofthe TPS and FPP sensors Exhaust System Checks Check the exhaust system for a possible restriction Inspect the exhaust system for damaged or collapsed pipes Inspect the muffler for signs of heat distress or for possible internal failure Check for possible plugged catalytic converter Engine Mechanical Check Check the engine for the following Engine compression Valve timing Improper or worn camshaft Refer to Engine Mechanical in the Service Manual Additional Check Check the ECU grounds for being clean tight and in their proper locations Check the generator output voltage If all procedures have been completed and no malfunction has been found review and inspect the following items Visually and physically inspect all electrical connections within the suspected circuit and or systems Check the scan tool data IMPCO Technologies Engine Service Manual 25 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Poor Fuel Economy DEFINITION Fuel economy as measured by refueling records is noticeably lower than expected Also the economy 15 noticeably lower than it was on this vehicle at one time as shown by an by refueling records Preliminary Checks Refer to Important Preliminary Checks Check the air cleaner element filter for dirt or being plugged Visually Physically check the vacuum hoses for splits kinks and proper connectio
102. P0172 or P0175 cont d Csee an Vales ve mw 1 Operate engine at idle 2 Using the scan tool observe HO2S parameters 200 800 mv Does the scan tool indicate that the values are within the specified range and fluctuating Go to Step 4 Go to Step 5 1 Turn OFF the engine Go to Step 7 Go to Step 6 2 Visually and physically inspect the following items Go to Fuel System Go to Step 7 Diagnosis Inlet screen of the MAF sensor for blockage Vacuum hoses for splits kinks and proper connections Refer to Emission Hose Routing Diagram The air intake duct for being collapsed or restricted The air filter for being dirty or restricted Check for objects blocking throttle body Did you find and correct the condition 1 Turn OFF the engine 2 Check the HO2S for proper installation 3 Check to ensure electrical connectors and wires are secured and not contacting the exhaust system Did you find and correct the condition Important After repairs use scan tool Fuel Trim Reset function in order to reset the Long Term Fuel 1 Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass With a scan tool observe the stored information Capture Info Does the scan tool display any DTCs that you have not diagnosed Go to Step 8
103. Refer to Pressure Trim Valve Replacement Disconnect the supply and return coolant lines from the LPR Remove the retaining pin from the water inlet and outlet fittings and retain Remove the coolant inlet and outlet fitting retaining pins and retain Remove the inlet fitting Remove the outlet fitting and retain Disconnect the FTV supply line Remove the two LPR mounting bolts and retain Lift LPR assembly and remove the two 2 LPR mount ing bolts and retain Loosen the fuel vapor hose clamp at the LPR fuel outlet fitting IMPCO Technologies Engine Service Manual 16 17 18 4 3 liter Emission Certified GM Engine Disconnect the fuel vapor hose from the LPR outlet fit ting and remove the LPR Remove the retaining pin from the vapor outlet fitting and retain Remove and retain the vapor outlet fitting from the LPR Remove the LPR Installation Procedure IMPORTANT 10 11 13 Do not use Teflon tape on any fuel fitting Use a lig uid pipe thread sealant when installing fittings Lubricate the o ring of the PTV before installing into the LPR Lubricate the o rings on each of the fitting Install the inlet water fitting and secure with retaining pin Install the outlet water fitting and secure with retaining pin Install vapor outlet fitting and secure with retaining pin Insert the vapor hose to the fuel outlet fitting and place clamp Install the FTV supply line and secure Secure the LPR t
104. Sd as Any problems found necessary Refer to Wiring Repairs in Engine Electrical mE IMPCO Technologies Engine Service Manual 147 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 148 5 volt reference pin 50 and engine ground Do you have continuity between them Using a DVOM check for continuity ECM connector 5 volt reference pin 50 and ECM sensor ground pin 49 Do you have continuity between them terminals for damage corrosion or contamination Any problems found Disconnect ECM wire harness connector C001 Using DVOM check for continuity between FPP connector signal pin C and ECM connector FPP signal pin 38 Do you have continuity between them Using a DVOM check for continuity connector FPP signal pin 38 and engine ground Do you have continuity Using a DVOM check for continuity ECM FPP signal pin 38 and ECM connector FPP sensor ground pin 49 Do you have continuity between them IMPCO Technologies Engine Service Manual epair circuit as necessary Refer to Wiring Repairs in Engine Ele trical circuit as necessary Refer to Wiring Repairs in Engine epair tf circuit as necessary Refer to Wiring Repairs in Engine Electrical o to Step 15 epalr the circuit as necessary Refer to Wiring Repairs in Engine epalr the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Refer to Wiring
105. Step 11 e Checkthat the ECM ground terminals G1 and G2 are clean and tight Are the ground terminals G1 and G2 clean and tight connector pin B and ECM connector pin 13 Do you have continuity between them e Inspect the CMP connector C011 terminals for damage corrosion or contamination Did you find a problem e Inspect the ECM connector C001 terminals 13 14 and 50 for damage corrosion or contamination Did you find a problem e Replace CMP sensor using R amp R procedure in Section 1E Pay special attention to CMP sensor reluctor wheel inspection Is the replacement complete e Replace ECM e 5 the replacement complete 1 Using a DVOM check for continuity between CMP IMPCO Technologies Engine Service Manual 89 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to Step 9 Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 145 check for any stored codes Does the engine operate normally with no stored codes Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC informa
106. System Diagnosis Fuel contamination Refer to Alcohol Contaminants in Fuel Diagnosis Without Special Tool or Alcohol Contaminants in Fuel Diagnosis With Special Tool Did you find and correct the condition Turn OFF the engine Check the HO2S for proper installation Check to ensure electrical connectors and wires are secure and not contacting the exhaust system Check for a short between the signal circuit and the low reference circuit Did you find and correct the condition Operate engine at idle Check for missing loose or leaking exhaust components forward of the HO2S Check for vacuum leaks at the intake manifold throttle body and injector O rings Check the air induction system and air intake ducts for leaks Check the secondary air injection AIR system for leaks improper air delivery or the shut off valve not closing Check the crankcase ventilation system for leaks Refer to Crankcase Ventilation System Inspection Diagnosis Did you find and correct the condition Step Go to Diagnostic Aids 23 Go to Step 3 200 800 mv Go to Step 4 BM IMPCO Technologies Engine Service Manual 9 Go to Step 5 Go to Step 6 Go to Fuel System Diagnosis Go to Symptoms Engine Mechanical in Engine Mechanical 4 3L 1C7 Ignition System 4 3 liter Emission Certified GM Engine DTC P0171 or P0174 cont d o Important After repairs use scan
107. T BLUE T8 53 PURPLELT BLUE TE 24 PINK WHITE 18 25 TAN ORANGE 18 37 LT GREEN BLACK 18 56 YELLOWILT GREEN IE 26 LTBLUE BLACK 18 47 BLACKWHITE 18 4 PURPLE DK BLUE TE 40 TAN SROWN 18 48 YELLOW DK BLUE TS 34 GRAY DK BLUE 18 15 WATERED 18 43 BLUE PINK 18 34 BLUE WHITE TE ST DK GREEN 18 52 ORANGE 18 27 YELLOWTS 29 BROWN WHITE 16 30 BROWN YELLOW 16 28 BROWN ORANGE 16 1 TANAT BLUE T6 Z REDAWHITE TB BLKLTGREEN18 p LTGREEN AEDIB C DK GREEN 18 B ORANGE 18 IMPCO Technologies Engine Service Manual LI GREEN RED 18 Ix Rx BROWN BLUE 16 5 e INJ ORANGEIRL 16 wr nn a E INJ __ GRAY BROWN 18 T BLK LT GREEN 18 o I c010 uraren COO9 II UI popptewane TE Je CRANK YELLOW BLACK 18 ____ mm a PINK DK GREEN 16 PLUG COIL MODULE BLK LT GREEN 18 n 1 BLK LT GREEN 18 3 DKBLUE 18 i ______ PINKWHITE 18 co12 GOVERNOR MOTOR TAN ORANGE 18 Tux YELOWGRAYS A co15 BACKATGMEN IS 8 ECT pe E pe M P rare LTOREEN 18 1 TREND TE d CO13 aeeoe G2 MOTOROLA TMAP scirem BOSCH TMAP m LPG ONLY ALTERNATOR GROUND
108. T GREEN 18 LT GREEN RED 18 PINK TAN 18 DK GREEN ORANGE 18 PURPLE WHITE 18 WHITE PURPLE 18 GRAY BROWN 18 PURPLE ORANGE 18 RED TAN 16 RED TAN 16 GRAY ORANGE 18 WHITE BLACK 18 TAN BLACK 18 WHITE LT BLUE 18 PURPLE LT BLUE 18 PINK WHITE 18 TAN ORANGE 18 LT GREEN BLACK 18 YELLOW LT GREEN 18 LT BLUE BLACK 18 BLACK WHITE 18 PURPLE DK BLUE 18 TAN BROWN 18 YELLOW DK BLUE 18 GRAY DK BLUE 18 WHITE RED 18 BLUE PINK 18 BLUE WHITE 18 DK GREEN 18 ORANGE 18 YELLOW 18 BROWN WHITE 16 BROWN YELLOW 16 BROWN ORANGE 16 TAN LT BLUE 16 RED WHITE 18 COMMUNICATION PORT C002 Pin Wire Color Function B Green RS2321X D Black Lt Green AnaRn IMPCO Technologies Engine Service Manual INJECTOR CONNECTOR C003 Pin Wire Color Function Bo Brown Green Injetor2 Do Brown Yellow lInector4 14 IMPCO Technologies Engine Service Manual INJECTOR CONNECTOR C004 Pin Wire Color Function Not Used D o WhiteBlak FuelLockoff IMPCO Technologies Engine Service Manual 15 OIL PRESSURE CONNECTOR C005 Lt Green Black 16 IMPCO Technologies Engine Service Manual TPS 1 CONNECTOR C006 Lt Green Red 5 Volt Ref B Black Lt Green Purple Lt Blue Throttle Position Sensor 1 IMPCO Technologies Engine Service Manual FPP CONNECTOR C006A Lt Green Red 5 Volt Ref 5 BlackiLt Green Dk Blue 18 IMPCO Technologies Engine Service Manual
109. TC 513 reset with the engine idling 3 Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical e Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 513 check for any stored codes Does the engine normally with no stored codes IMPCO Technologies Engine Service Manual 125 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 514 RTI 1 Loss Microprocessor Conditions for Setting the DTC Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM runs checks that must be verified each time an instruction is executed Several different things can happen within
110. TC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 631 check for any stored codes Does the engine operate normally with no stored codes 152 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 153 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 632 TPS 1 Signal Voltage Low LT GRN RED 5 volts PPL LT BLUE Signal BLK LT Sensor Ground Conditions for Setting the DTC Throttle Position Sensor 1 Check Condition Cranking or Running Fault Condition TPS sensor voltage less than 0 2 MIL On during active fault 9 Engine Shut Down Circuit Description The Electronic Throttle has two counter acting Throttle Position Sensors Two sensors are used for improved safety and redundancy The Throttle Position sensor uses a variable resistor to determine signal voltage based on throttle plate position and is located within the throttle Less opening results in lower voltage and greater opening in higher voltage The TPS value is used by the ECM to determine if the throttle is opening as commanded This fault will set if voltage is less than 0 2 volts at any operating con
111. Trouble Codes 1C4 DTC 131 MAP HIGH PRESSURE Bosch _ Value s Yes No o to tep o to OBD System Check Section j to step Intermittent e Key On Engine running problem DST Diagnostic Scan Tool connected in Go to System Data Mode Intermittent section Does DST display MAP pressure of 13 0 psia or greater with the engine idling e Key OFF o to step 4 o to step 6 e Disconnect the TMAP sensor connector e Key ON Does the DST display MAP pressure less than 0 05 psia e Probe TMAP sensor connector ground circuit pin o lo 5 o lo 1 with a est light connected to battery voltage Repair the Disconnect ECM connector and inspect terminals circuit as for damage corrosion or contamination Is the necessary connection OK Refer to Wiring Repairs in Engine ma o to step 9 Repair the continuity between TMAP connector sensor circuit as ground pin 1 and ECM sensor ground PIN 49 necessary Do you have continuity between them Refer to Wiring Repairs in Engine Electrical Replace Refer to M replacement in the o to step nn Controls Section t VIA IMPCO Technologies Engine Service Manual 49 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine emove all test equipment except the 051 ystem OK Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and
112. ack Lt Green __ IMPCO Technologies Engine Service Manual 27 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi STARTER RELAY C016 87A Lt Blue Pink Start In Interrupt Type Pink Black Start In Autocrank 86 Pink Tan VSW Fuse F1 Grey Orange Starter Solenoid 28 IMPCO Technologies Engine Service Manual POWER RELAY C017 Pink Dk Green Alternator Fuse F3 86 Red Tam ECMVBAT White Blue Relay Control 30 Red Battery IMPCO Technologies Engine Service Manual 29 1C2 Wirina Sci ti 1 3 liter Emission Certified GM Engi FUEL PUMP RELAY C018 Pink Yellow Fuel Pump 86 ___ Pink Tan VSW Fuse F1 Tan Black ECM Fuel Pump 30 IMPCO Technologies Engine Service Manual BATTERY CONNECTOR C019 Pin Wire Color Function A Red jBate IMPCO Technologies Engine Service Manual 31 ALTERNATOR CONNECTOR C020 Pin Wire Color Function A Red Batey 32 IMPCO Technologies Engine Service Manual ALTERNATOR CONNECTOR C021 Pin Wire Color Function JA JRed Battey IMPCO Technologies Engine Service Manual 33 1C2 Wiring Sci ti 1 3 liter Emission Certified GM Engi INSTRUMENT PANEL CONNECTOR C022 ns 0 0 A Pin Wire Color Function B DkBue FPP D Black Lt Green Ana Return E NotUsed H
113. agnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged nspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 113 IAT Higher Than Expected 1 Motorola TMAP Diagnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged Inspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system If none of the above can be found Follow the diagnostic steps for 112 IAT Low Voltage IMPCO Technologies Engine Service Manual 29 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 114 IAT Higher Than Expected 2 Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition Intake Air Temperature greater than 220 degrees F and engine RPM greater than1000 MIL On for active fault and for 15 seconds after active fault Adaptive Disabled during active fault Cl
114. agnostic Trouble Codes stored in the memory of the Spectrum system ECM using a diagnostic jumper and the Malfunction Indicator Lamp With the key off connect the diagnostic jumper to the ECI system diagnostic connector located near the ECM The jumper will connect diagnostic pins A and D Turn the ignition on but do not start the vehicle The Malfunction Indicator Lamp MIL will begin to flash 10 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 The MIL displays three digit codes by flashing the first digit pausing then flashing the second digit pausing and then flashing the third digit There will be a long pause between codes For example a code 143 would be one flash followed by four flashes followed by three flashes The MIL will first display a 123 three times Code 123 indicates that the ECM based diagnostic routines are functioning Then any Diagnostic Trouble Codes stored in memory will display three times each The MIL will then start over with the code 123 If the vehicle is started while the diagnostic jumper is in place the MIL will flash rapidly Diagnostic Trouble Codes may be cleared from the system ECM memory by moving the ignition key to the OFF position and removing the F1 system battery fuse for at least 15 seconds Note This will erase all of the memory in the computer including the adaptive learn DIAGNOSTIC PROCEDURES FOR BI FUEL APPLICATIONS Diagnosti
115. ained by the amount of pressure applied to a foot pedal located in the operator s compartment A cable is utilized to connect the foot pedal to the throttle shaft in the engine compartment A coil spring mounted to the pedal and the throttle shaft will keep the throttle shaft in a normally closed position When the foot pedal is depressed the throttle shaft is rotated opening the butterfly in the ven turi of the throttle body allowing more air to enter the engine When the ECM detects that the engine has reached maximum governed speed or requires adjustment for load the ECM will correct the blade position by overriding the throttle shaft with the electronic governor IMPCO Technologies Engine Service Manual 3 1A2 Fuel System Operation The Throttle Control device or throttle body assembly is connected to the intake manifold of the engine The Throttle body maintains control of engine speed by increasing or de creasing the opening angle of the throttle blade in the throttle body bore thus increasing or decreasing the intake air to the engine The throttle blade shaft is connected to a spring loaded cable connector which is connected to the foot pedal in the operator s compartment The shaft incorporates a return spring to insure the blade position returns to idle when the operator removes his foot from the pedal Also attached to the throttle shaft is a Throttle Position Sensor TPS which provides a signal to the ECM to i
116. air the circuit Disconnect ECM connector C001 USE Using aDVOM check for continuity between CMP Refer Wiring Repairs in Engine Electrical Go to Step 6 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to Step 7 as necessary Refer to Wiring Repairs in Engine Electrical connector pin Aand ECM connector pin 14 Do you have continuity between them Repair the circuit Go to step 8 as necessary Refer to Wiring Repairs in Engine Electrical m mE Go to Step 11 e Check that the ECM ground terminals G1 and G2 are clean and tight Are the ground terminals G1 and G2 clean and tight connector pin B and ECM connector pin 13 Do you have continuity between them e Inspect the CMP connector C011 terminals for damage corrosion or contamination Did you find a problem e Inspect the ECM connector C001 terminals 13 14 and 50 for damage corrosion or contamination Did you find a problem e Replace CMP sensor using R amp R procedure in Section 1E Pay special attention to CMP sensor reluctor wheel inspection Is the replacement complete e Replace ECM e 5 the replacement complete 1 Using a DVOM check for continuity between CMP IMPCO Technologies Engine Service Manual 85 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to Step 9 Connect any disconnected components fuses
117. al engine can utilize any type of permanent antifreeze or any brand antifreeze solution that meets GM Specification 1825M or 1899M which will not damage alumi num parts ENGINE ELECTRICAL SYSTEM MAINTENANCE The engine electrical system incorporates computers to con trol certain functions of the equipment The electrical system connections and ground circuits require good connections Follow the recommended maintenance schedule in this sec tion to maintain optimum performance When inspecting the electrical system check the following e Check battery connection clean and insure that connectors are tight e Check battery for cracks or damage to the case replace if necessary e Check Positive and Negative cables for corrosion rubbing chaffing and insure tight connections at both ends e Check engine wire harness for rubbing chaffing pinching and cracks or breaks in the wiring e Check engine harness connectors check to insure fitted and locked by pushing the connector together then pull on the connector halves to insure they are locked e Check ignition coil wire for hardening cracking arcing chaffing separation split boot covers and proper fit e Check spark plug wires for hardening cracking chaffing separation split boot covers and proper fit e Replace spark plugs at the required intervals per the recommended maintenance schedule e Check to insure all electrical components securely mounted and re
118. al pair it is possible to dam age certain components Always use jumper wires between connectors for circuit checking NEVER probe through the Weather Pack seals Use tachometer adapter 35812 or TWISTED SHIELDED CABLE 1 REMOVE OUTER JACKET 2 UNWRAP ALUMINUM MYLAR TAPE DO NOT REMOVE MYLAR Ra 3 UNTWIST CONDUCTORS STRIP INSULATION AS NECESSARY UNI 4 SPLICE WIRES USING SPLICE CLIPS AND ROSIN CORE SOLDER WRAP EACH SPLICE TO INSULATE 5 WRAP WITH MYLAR AND DRAIN UNINSULATED WIRE 1111 7 6 TAPE OVER WHOLE BUNDLE TO SECURE AS BEFORE equivalent which provides an easy hook up of the tach lead The connector test adapter kit J 35616 or equivalent contains an assortment of flexible connectors used to probe termi nals during diagnosis Fuse remover and test tool BT 8616 or equivalent is used for removing a fuse and to adapt fuse holder with a meter for diagnosis When diagnosing open circuits are often difficult to locate by sight because oxidation or terminal misalignment are hidden by the connectors Merely wiggling a connector on a sensor or in the wiring harness may correct the open circuit condi tion This should always be considered when an open circuit or failed sensor is indicated Intermittent problems may also be caused by oxidized or loose connections Before making a connector repair be certain of the type of connector Weather Pack and Compact Three connectors lo
119. amage corrosion or contamination Did you find a problem e Replace CKP sensor using CKP R amp R procedure in Section 1E Pay special attention to CKP reluctor wheel inspection Is the replacement complete e Replace ECM e 5 the replacement complete 1 Using a DVOM check for continuity between CKP IMPCO Technologies Engine Service Manual 81 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to Step 9 Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 143 check for any stored codes Does the engine operate normally with no stored codes Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 143 check for any stored codes Does the engine operate normally with no stored codes 82 IMPCO Technologies Engine Service Manual
120. ank the engine The test light should illumi nate Remove the LPG fuel filter LPL Remove the filter from the LPL Empty the contents of the inlet side of the LPG fuel filter onto a clean surface Inspect the contents of the LPG fuel filter for an excessive amount of foreign material or water If necessary locate and repair the source of contamination Verify the LPG fuel filter is not restricted or plugged Was a problem found Replace the fuel filter Refer to Fuel Filter Replacement Is the action complete Repair the open in the lock off ground circuit Is the action complete Repair the open in the lock off power OEM fuel pump circuit Is the action complete Replace the low pressure regulator LPR Refer to Low Pressure Regulator Replacement Go to Step 26 Go to Step 26 Go to Step 26 IMPCO Technologies Engine Service Manual 5 Is the action complete Replace the lock off Refer to Low Pressure Lock off LPL Replacement Is the action complete Replace the mixer assembly Refer to Fuel Mixer Replacement Is the action complete The fuel supply system or hoses are plugged or re stricted locate and repair the problem Is the action complete 1B1 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine The fuel supply system is operating normally if a failure of the control solenoids is suspected Refer to Fuel Control System Diagnosis Install the test plug in the LPR se
121. ark plug wires by connecting an ohmmeter to the ends of each wire in question If the meter reads over 30 000 ohms replace the wires Additional Checks Check the ECU grounds for being clean tight and in their proper locations Check the battery cables and ground straps They should be clean and secure Erratic voltage may cause all sensor readings to be skewed resulting in poor idle quality Engine Mechanical Check Check the engine for the following Broken motor mounts Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes IMPCO Technologies Engine Service Manual 27 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Surges Chuggles DEFINITION The engine has a power variation under a steady throttle or cruise The vehicle feels as if it speeds up and slows down with no change in the accelerator pedal Preliminary Checks Referto Important Preliminary Checks e sure the driver understands the Torque Converter Clutch operation Sensor Checks Check the Heated Exhaust Gas Oxygen Sensor HEGO performance Fuel System Checks e Check for Rich or Lean symptom that causes the condition Drive the vehicle at the speed of the complaint Monitoring the oxygen sensors will help identify the problem Check the fuel rail pressure while the condition exists Refer to Gasoline Fuel System Diagnosis Verify check injector electrical connections Check
122. ark plugs are correct for use with LPG R42LTS Check the spark plugs Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Check the Crankshaft Position CKP sensor Check the ECU grounds for being clean tight and in their proper locations Check the generator output voltage Check the vacuum hoses for kinks or leaks Check Transmission IMPCO Technologies Engine Service Manual 15 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine GASOLINE SYMPTOM DIAGNOSIS Symptom Diagnosis Important Preliminary Checks Before Using This Section Before using this section you should have performed On Board Diagnostic Check and determined that 1 The Control Module and MIL Malfunction Indicator Lamp are operating correctly There are no Diagnostic Trouble Codes DTCs stored or a DTC exists but without a MIL Several of the following symptom procedures call for a careful visual and physical check The visual and physical checks are very important The checks can lead to correcting a problem without further checks that may save valuable time LPG Fuel System Check Verify the customer complaint Locate the correct symptom table Check the items indicated under that symptom Operate the vehicle under the conditions the symptom occurs Verify HEGO switching between lean and rich IMPORTANT Normal HEGO switching indicates the Gas
123. art Have any other DTC codes been detected diagnosed and repaired Replace HO2S sensor s the replacement complete Remove all test eguipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 242 check for any stored codes Does the engine operate normally with no stored codes Key OFF Disconnect HO2S sensor wire harness connector Disconnect ECM wire harness connector Key ON Using a DVOM check for voltage at HO2S connector signal pin B and engine ground NECEM to ET 3 Goto Step 2 Go to Step 7 Go to Step 4 Go to Step 7 Go to step 4 Repair the Go to Step 5 circuit as necessary Refer to Wiring Repairs in Engine Electrical System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 109 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 243 Adaptive Learn High LPG Sensor Ground Heater To System Power Relay To Engine Ground Conditions for Setting the DTC Heated Oxygen Sensor Check Condition Engine Running Fault Condition Adaptive multiplier out of range greater than 30 MIL Disabled Adaptive Enabled Closed L
124. ay as long as the engine is cranking or running and crankshaft reference pulses are received If no crankshaft reference pulses are received the PCM de energizes the fuel pump relay after 2 seconds The PCM monitors the voltage on the fuel pump relay control circuit If the PCM detects an incorrect voltage on the fuel pump relay control circuit diagnostic trouble code DTC P0230 sets Conditions for Running the DTC The engine speed is more than 400 RPM The ignition voltage is between 6 18 volts Conditions for Setting the DTC stores this information in the Failure Records If the diagnostic reports a failure on the second consecutive ignition cycle the control module records the operating conditions at the time of the failure The control module writes the operating conditions to the Freeze Frame and updates the Failure Records Conditions for Clearing the MIL DTC e The control module turns OFF the malfunction indicator lamp MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail A current DTC Last Test Failed clears when the diagnostic runs and passes A history DTC clears after 40 consecutive warm up cycles if no failures are reported by this or any other emission related diagnostic Use a scan tool in order to clear the MIL and the DTC e e e The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match Test Desc
125. be on and the engine will shut down IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 637 Throttle Unable to Open Sup uo Ye no Did you perform the On Board OBD System Check NM mai Go to OBD System Check Section Key ON Engine OFF Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem DBW Drive By Wire test mode Go to Depress Foot Pedal until theThrottle Command is Intermittent 63 68 section Is the TPS voltage less than 2 0 volts Key OFF Go to Step 4 Go to Step 8 Disconnect wire harness connector from throttle Probe TPS 1 signal circuit with test light connected to battery voltage Key ON Is TPS voltage 4 0 volts or greater 4 e Check throttle bore for foreign object Go to Step 5 Go to step 6 Did you find a problem 5 e Remove the foreign object Go to Step 11 Has the object been removed e Check throttle connector terminals for damage Repair the Go to Step 7 corrosion or contamination circuit as Did you find a problem necessary Refer to Wiring Repairs in Engine Electrical Replace throttle Go to Step 11 Is the replacement complete Key OFF Go to Step 9 Repair the Disconnect ECM wire harness connector circuit as Using a DVOM check for continuity between necessary throttle connector TPS 1 signal terminal and ECM Refer to TPS 1 signal terminal Wiring Repairs Do you have continuity
126. between TMAP sensor as necessary connector signal circuit pin D and ECM signal PIN Refer to Wiring 33 Repairs in Engine Do you have continuity between them Electrical Check for continuity between TMAP sensor Repair the circuit Go fo step 15 connector signal pin D and engine ground as necessary Do you have continuity Refer to Wiring Repairs in Engine Electrical Inspect ECM connector and wire harness Repair the circuit Go to Step 16 connector terminals for corrosion contamination as necessary or mechanical damage Refer to Wiring Any problems found Repairs in Engine Electrical Replace ECM Refer to ECM replacement in the Go to Step 18 Engine Controls Section Is the replacement complete Replace TMAP sensor Go to step 17 17 Is the replacement complete 62 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 Remove all test eguipment except the DSC System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 132 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 63
127. between them kaki e Using a DVOM check for continuity between Repair the Go to Step 10 throttle connector TPS 1 signal and engine ground circuit as Do you have continuity between them necessary Refer to Wiring Repairs in Engine Electrical 10 e Replace ECM Go to step 11 Is the replacement complete IMPCO Technologies Engine Service Manual 157 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 637 check for any stored codes Does the engine operate normally with no stored codes 158 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 159 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 638 Throttle Unable To Close PNK WHT DBW 24 Cd Hat m Ted PPL LT BLU TPS 1 Signal MM C 53 H BLK LT GRN Sensor Ground FPP DK BLU FPP Signal ua 38 5 VOLTS ECM Conditions for Setting the DTC Throttle Position Sensor Check Conditio
128. bility After operating the engine within the test parameters of DTC 652 check for any stored codes Does the engine operate normally with no stored codes 7 e Correct mechanical operation of the throttle Refer Go to step 9 to Engine amp Component R amp R Section 1E Has the mechanical operation of the throttle been corrected 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 653 Spark Rev Limit PNK WHT DBW 24 u TAN ORN n PPL LT BLU TPS 1 Signal 53 BLK LT GRN Sensor Ground DK BLU FPP Signal 38 5 VOLTS LT GRN RED ECM Conditions for Setting the DTC Spark Rev Limit Check Condition Engine running Fault Condition Engine RPM greater than 4100 for 2 seconds continuously MIL On during active fault Adaptive Enabled Closed Loop Enabled Circuit description This fault will set anytime the engine RPM exceeds 4100 for 2 seconds or more continuously When these conditions are met the ECM will shut off spark to the engine This is to help prevent engine or equipment damage The MIL will be on during this active fault 168 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 653 Spark Rev Limit Sten Aten Vau Ye Ne Did you perform the On Board OBD System Check Go to 2 Go to OBD System Check Section Go to Step 3 Go to Step 4 u Go to Step 6 Go to Step 5
129. ble in both analog and digital types May be referred to as AVOM and DVOM Voltage The electrical pressure that causes current to flow in a circuit Measured in volts Voltage Drop A lowering of the voltage in a circuit when resistance or electrical load is added Xylene C6H4 CH3 2 Any of three toxic flammable oily isomeric aromatic hydrocarbons that are dimethyl homologues of ben zene and are usually obtained from petroleum or natural gas distillates ZEV Zero Emission Vehicle 6 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Maintenance OB SECTION OB MAINTENANCE IMPCO Technologies Engine Service Manual 1 OB Maintenance 4 3 liter Emission Certified GM Engine MAINTENANCE The maintenance of the engine and its related components is critical to the life of the engine and optimum performance during its useful life engines reguire a certain amount of maintenance The suggested maintenance reguirements are contained in this section Industrial engines operate in vari ous environments from extremely dusty environments to hot and cold temperature environments and clean environments The recommended schedule is a recommended guide line for the owner and servicing agency to follow however certain en vironmental operating conditions may reguire more freguent inspection and maintenance In addition the owner may have installed additional eguipment to the eguipment which may also increa
130. c Trouble Codes DTC will set in both propane and gasoline fuel modes Some DTC s are specific to either gasoline or propane but are described in the DTC charts as such When dealing with a fuel specific DTC it is advised to run the diagnostic test in the fuel mode that the code was originally set In the case of a fuel specific DTC the diagnostic test procedures must be performed running in the fuel mode that is described for that particular DTC An example of this would be DTC 243 Adaptive Learn High LPG The diagnostic test must be run in the LPG mode for a successful repair In the presence of multiple DTC codes always begin with the lowest number DTC and diagnose each problem to correction unless directed to do otherwise by the DTC chart The DTC s are numbered in order of importance Having DTC 112 and DTC 122 both concerning the oxygen sensor is possible By repairing DTC 112 first the problem causing the DTC 122 may also be corrected When a is set the ECM will illuminate the Malfunction Indicator Lamp on the instrument panel and save the code in memory The ECM will continue to run the self test unless the DTC is an oxygen sensor lean oxygen sensor rich or an internal ECM related If the system continues to fail the test the lamp will stay illuminated and the DTC is current ACTIVE All DTC s are stored as historical faults until they are cleared DTC s except the ECM related DTC s will automatically clear from mem
131. cal Replace ECM Go to Step 4 Is the replacement complete Remove all test eguipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 511 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 121 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 512 Invalid Interrupt Microprocessor Conditions for Setting the DTC Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM has checks that must be verified each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Powe
132. ce pin 3 and engine circuit as ground necessary Do you have continuity Refer to Wiring Repairs in Engine M connector pins for Repair the o to Step 16 corrosion contamination or mechanical damage circuit as Any problems found necessary Refer to Wiring Repairs in Engine Replace Refer to M replacement in the o to step 17 Engine Controls Section D t ECV 00 o fo Step 14 epair the Check for continuity between TMAP sensor circuit as connector pin 4 and ECM pin 33 necessary Do you have continuity between them Refer Wiring Repairs in Engine Electrical y epair the o to step 15 connector pin 4 and engine ground circuit as Do you have continuity necessary Refer to Wiring Repairs connector pins for corrosion contamination or circuit as mechanical damage necessary Any problems found Refer to Wiring Repairs in Engine Electrical D o to step 17 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 emove all test equipment except the DST ystem OK Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 135 check for any stored codes Does the engine
133. commutator end frame Place washer and commutator end frame onto shaft IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine SNAP RING 22664 013 Figure 4 8 Assembling Overrunning Clutch to Armature 4 3 liter Emission Certified GM Engine 22664 014 Figure 4 9 Disconnecting Field Coil From Solenoid Strap 6 Install through bolts and tighten securely 7 Install solenoid return spring on plunger 8 Position solenoid assembly to starter motor end frame and turn solenoid to engage flange in slot 9 Install screws which hold solenoid assembly to end frame and tighten securely 10 Install field coil screw and tighten securely STARTER MOTOR ADJUSTMENTS Figures 4 9 through 4 11 Pinion Clearance Pinion clearance must be checked as follows after reassembly of motor to insure proper adjustment 1 Disconnect motor field coil connection from solenoid motor terminal and insulate it care fully figure 4 9 2 Connect 12 volt battery from solenoid switch terminal to solenoid frame Starter 1C5 BATTERY Le TERMINAL CRANKING PER MOTOR TERMINAL 22664 015 Figure 4 10 Shifting Starter Pinion to Check Clearance PINION RETAINER FEELER GAUGE 22664 016 Figure 4 11 Checking Starter Pinion Clearance 3 Momentarily touch a jumper lead from sole noid motor terminal to starter motor frame figure 4 10 This shifts pinion into crankin
134. complete e Key OFF Repair the Go to step 6 5 e Disconnect ECM wire harness connector circuit as Check for continuity between ECT sensor necessary connector signal pin A and ECT sensor ground Refer to pin B Wiring Repairs Do you have continuity between them 5 Engine Electrical Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature uu NEM System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 43 Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 122 check for any stored codes Does the engine operate normally with no stored codes e Check for continuity between ECT sensor Go to step 7 connector signal circuit pin A and engine ground Repair the Do you have continuity circuit as necessary Refer to Wiring Repairs in Engine Electrical 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 123 ECT Higher Than Expected 1 Sensor Ground ECM Conditions for Setting the DTC 9 Engine Coolant Temperature Check Condition Engine Running Fault Condition Engine Coolant Tem
135. condary chamber If you were sent to this routine by another diag nostic chart return to the previous diagnostic procedure Is the action complete System OK Disconnect all test equipment Install the primary and secondary test port plugs Start the engine Using an approved liguid leak dtector check the test port plugs System OK Is the action complete 6 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine FUEL CONTROL DIAGNOSIS STEP ACTION VALUE S 1 Were you referred to this procedure by an other diagnostic chart Are any DTC s present in the ECM 3 Has the Fuel Ssytem diagnosis been per formed 1 Connect the Diagnostic Scan tool 2 Start the engine and allow it to reach oper ating temperature 3 With the engine idling observe the duty cycle reading of the PTV on the scan tool OR Back probe the PTV connector Connecta duty cycle monitoring tool at the PTV connec tor as follows IMPCO FSA 2 Perform the On Board Diagnostic OBD Go to Applicable System check DTC Table Yellow clip to pin B 20 80 Green Clip not used for this test Red clip to 12V battery positive Black Clip to battery negative DVOM Back probe the PTV connector Set the DVOM for duty cycle percentage and connect between pin B and battery negative ground LPG Fuel System Diagnostics 1B1 Go to Step Go to Step 2 jGoteStp 3 Go to Fuel system Diagnosis GotoSt
136. conds SIO ID 727820 Action Taken When the DTC Sets The control module illuminates the malfunction indicator lamp MIL on the second consecutive ignition cycle that the diagnostic runs and fails The control module records the operating conditions at the time the diagnostic fails The first time the diagnostic fails the control module stores this information in the Failure Records If the diagnostic reports a failure on the second consecutive ignition cycle the control module records the operating conditions at the time of the failure The control module writes the operating conditions to the Freeze Frame and updates the Failure Records SIO ID 727824 Conditions for Clearing the MIL DTC The control module turns OFF the malfunction indicator lamp MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail A current DTC Last Test Failed clears when the diagnostic runs and passes A history DTC clears after 40 consecutive warm up cycles if no failures are reported by this or any other emission related diagnostic Clear the MIL and the DTC with a scan tool Diagnostic Aids Performing the Fuel Injector Coil Test may help isolate an intermittent condition Refer to Fuel Injector Coil Test e For an intermittent condition refer to Intermittent Conditions Test Description The numbers below refer to the step numbers on the diagnostic table 4 This step test
137. content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the adaptive multiplier This fault sets if the Closed Loop multiplier exceeds the limits of normal operation When the multiplier cannot correctly modify the fuel flow within its limits it is limited at 35 Diagnostic Aids Always diagnose any other ECM codes that are present before beginning this diagnostic procedure Fuel System High secondary fuel pressure can cause the system to run rich A worn fuel mixer faulty PTV pressure trim valve or FTV fuel trim valve can also cause the system to run rich Fuel Quality A drastic variation in fuel quality very high butane content may cause the system to run rich Be sure that the specified HD 5 or HD 10 motor fuel grade propane is used 102 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 224 Closed Loop Multiplier Low a Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine to full operating temperature and then idle for a minimum of 2 minutes Does DST display HO2S voltage fixed above 0 7 volts after 2 minutes of idle run time Key OFF Disconnect HO2S wire harness connector Disconnect ECM wiring harness connector Key ON Using a high impedance DVOM check for voltage between HO2S connector signal pin B and engine ground Do you have voltage
138. ction Indicator Lamp MIL Loss of DTC Memory Additiona ec Refer to Important Preliminary Checks Do not use the DTC tables If a fault is an intermittent the use of the DTC tables may result in the replacement of good parts Faulty electrical connections or wiring can cause most intermittent problems Check the suspected circuit for the following conditions Faulty fuse or circuit breaker Connectors poorly mated Terminals not fully seated in the connector backed out Terminals not properly formed or damaged Terminal to wires poorly connected Terminal tension insufficient Carefully remove all the connector terminals in the problem circuit in order to ensure the proper contact tension If necessary replace all the connector terminals in the problem circuit in order to ensure the proper contact tension Checking for poor terminal to wire connections requires removing the terminal from the connector body If a visual and physical check does not locate the cause of the problem drive the vehicle with a scan tool When the problem occurs an abnormal voltage or scan reading indicates the problem may be in that circuit The following components can cause intermittent MIL and no DTC s e A defective relay Control Module driven solenoid or a switch that can cause electrical system interference Normally the problem will occur when the faulty component is operating The improper installation of electrical devices such as lights 2
139. ction Systems FUEL SYSTEM DESCRIPTION The Engine Control Module ECM receives information from various engine sensors in order to control the operation of the fuel injectors The electric fuel pump prevents fuel flow unless the engine is cranking or running During key on electric fuel pump receives a two 2 second prime pulse from the ECM which allows Gasoline to flow from the tank through fuel filter and fuel lines to the fuel rails where the pressure is regulated With Ignition ON and fuel pump run ning pressure should be 284 325 kPa 41 47 psi When the engine is idling manifold pressure is low high vacuum and is applied to the pressure regulator diaphragm Vacuum will offset the spring pressure and result in very low fuel pressure Fuel pressures at idle will vary somewhat de pending on barometric pressure but should be less then pump pressure Unused fuel is returned to the fuel tank by a separate return fuel line The fuel pump pressure test port is located on the fuel rail Diagnostic Aids 2 IMPCO Technologies Engine Service Manual This procedure is intended to diagnose a vehicle operating on Gasoline Ifthe vehicle will not continue to run on Gasoline refer to Hard Start for preliminary checks Before proceeding with this procedure verify that the vehicle has a sufficient quantity of fuel Tools Required e J34730 1 or equivalent e J 37287 or equivalent Diagnostic Scan Tool e IMPCO fuel sys
140. ctional part ar row pointing to mixer 10 Reinstall the small hose section and set clamps 11 Start engine and check for leaks 8 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine PTV HOSE REPLACEMENT 1 Using a hose clamp pliers disconnect the clamps on the hose fitting at the mixer 2 Usinga small screw driver push locking clip back on PTV connection 3 Remove the hose and discard Installation Procedure IMPORTANT e PTV hoses are specifically designed DO NOT use hose material or length other than the OEM speci fied parts Install hose clamps and set back on the mixer hose end Reinstall hose at the PTV and push lock in place Reinstall hose at the mixer and set clamp au Start engine and check for leaks FTV HOSE REPLACEMENT 1 Using a small screw driver push locking clips back on FTV connection at FTV and LPR 2 Remove the hose and discard Installation Procedure IMPORTANT e FTV hoses are specifically designed DO NOT use hose material or length other than the OEM speci fied parts 3 Reinstall hose at the PTV and LPR and push locks in place 4 Start engine and check for leaks ENGINE CONTROL MODULE REPLACEMENT 1 Disconnect Negative battery cable 2 Remove controller from mounting bracket 3 Push connector lock back to unlock connector 4 Unplug controller and remove Installation Procedure IMPORTANT Controller is calibrated for each engine verify you ha
141. ctive fault is no longer present the MIL light will flash at 2 Hz for the remainder of the key on cycle This is a reminder that the Low Rev Limit is still enforced IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 611 FPP Voltage High Step 6 ooo Value s Yes No e DST Diagnostic Scan Tool connected in System Data Mode Disconnect sensor connector Inspect connector and wire terminals for damage corrosion or contamination Any problems found e Check continuity between FPP sensor connector ground pin B and ECM connector FPP sensor ground pin 49 Do have continuity between them ey ON e Using a DVOM check for voltage at ECM wire harness connector FPP signal pin 38 and ECM sensor ground terminal pin 49 Do you have voltage between them harness connector between ECM FPP signal pin 38 and engine ground Do you have voltage between them eyO Disconnect FPP sensor from wire harness Using a DVOM check for voltage between the ECM FPP signal pin 38 and engine ground Do you have voltage between them e heplace Is the replacement complete circuit as necessary Refer to Wiring Repairs in Engine Electrical epair the circuit as necessary Refer to Wiring Repairs in Engine epair if circuit as necessary Refer to Wiring Repairs in Engine Electrical o to Step epalr the circuit as necessary R
142. d and locked Check to insure that the fuel storage cylinder is positioned with the locating pin in the tank collar on all hori zontally mounted cylinders this will insure the proper func tion of the cylinder relief valve When refueling or exchanging the fuel cylinder check the quick fill valve for thread damage Insure the o ring is in place check the o ring for cracking chunking or separation replace if damaged before filling Check the service line quick coupler for any thread damage Insure the o ring is in place check the o ring for cracking hardening chunking or separation Replace if damaged IMPORTANT When refueling the fuel cylinder wipe clean both the female and male connection with a clean rag prior to filling This will prevent dust dirt and debris from being introduced to the fuel cylinder and prolong the life of fuel filter IMPCO Technologies Engine Service Manual 5 OB Maintenance 4 3 liter Emission Certified GM Engine INSPECTION AND REPLACEMENT OF THE FUEL FILTER The Propane system on this emission certified engine utilizes an in line replaceable fuel filter element This element should be replaced at the intervals specified in the recommended maintenance schedule When inspecting the fuel filter check the following Check for leaks at the inlet and outlet fittings using a soapy solution or an electronic leak detector if leaks are detected make repairs Check to make sure filter is secur
143. d loop multiplier while each driver is disabled IMPCO Technologies Engine Service Manual 9 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine EDIS ECI Serial Communications O 18 x File Page Flash CommPort Plot Log Help Fat Pon rm Control and hs runenta oa Specialists _Toggle Cel F10 ze ur Sysem suns ETT A CT ee Engine Speed m Run Mode Stopped TPS command 00 x firing order dwelms fing order voltage voltage Manifold Pressure 1438 psia Fuel Type CERVUS TPS position 01 X 1 425 1 o 14 Coolant Temperature 1133 degF Fuel Control Mode pen Loop FPP command 00 X 2 425 2 oig 134 Cylinder Head Temp 1133 degF Governor switch state Govd FPP position 00 X 3 000 02 134 Manitold Temperature 1133 degF Active govemor type Min TPS1 voltage 0 489 vols 4 w 4 Intake Air Temperature 81 5 degF Active governor mode Droop TPS2 voltage 4472 volts s oof oo Vbat 128 volts Brake input level Open FPP1 voltage 0451 volts 6 oof 00 Vsw 125 vots Dil pressure state LESSE FPP2 voltage 0000 vols Hour meter 12858 hous IVS voltage 5000 vols Cumulative starts 39 starts Closed Loop Contro Digital input Voltages Diagnostic Modes EGOI 0000 vots Fuelselectvolage 104 vols Spark kil Normal v Closed loop 1 E Fuel pump voltage 00 vols il Normal v Adaptive 1 00 Gov1 voltage 205 vols Enabled w Gov2 voltage 206 vols
144. d pin and ECM sensor ground PIN 49 Do you have continuity between them Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete e Correct TMAP mechanical connection Has TMAP mechanical connection been corrected Step To Vau Ye Ne Did you perform the On Board OBD System Check Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent section Go to step 4 Go to step 6 Go to step 5 Go to step 8 Go to Step 2 Go to step 7 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Go to step 11 Go to step 9 Go to step 11 Go to Step 11 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical EE Go to step 6 Go to Step 10 IMPCO Technologies Engine Service Manual 53 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 131 check for any stored codes Does the engine operate normally with no stored codes
145. diagnostics IMPCO Technologies Engine Service Manual 5 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DATA STREAM EDIS ECI Serial Communications File Page Flash Comm Port Plot Log Help Gauges Ford Power Products ECM Interface Inc Contra and instrumentation Spaciaists Link error attempting reconnect Connected at 19200 bps System Vanables Coolant Temperature Intake Air Temperature Manifold Pressure 250 250 Engine Speed 2498 rpm 200 200 Min Setpoint 1000 pm 150 150 Max Governor Setpoint 4500 pm 100 100 50 50 Pulse width 432 ms 0 0 EGO vots 50 50 EGO2 0 452 volts 47 psia um degF 77 degF Hour meter 12484 hours Cumulative starts 37 starts Foot Pedal Position Throttle Position 1 v 1 mi Battery Voltage System State 60 60 50 100 150 Run Mode Running 40 40 0 0 Power Mode gU 20 Fuel Type Gasoline i o 18 vole FuelControlMode CLActve 17 perje Governor switch state Gova oo Active governor type Min Active governor mode Droop Oil pressure state OK Reading Sensor and Actuator Values Most applicable sensor and actuator values are displayed on the Gauges screen The display shows the value for sensors voltages and the sensor values in engineering units NOTE If a DTC for a sensor is current the engineering value for
146. dition while the engine is cranking or running The engine will not start or run during this active fault 154 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 632 TPS 1 ar Voltage Low OBD System Check System check ection o to Mn 4 o to Step DST Diagnostic Scan Tool connected in DBW Drive by Wire throttle test mode pes the DST TPS 1 voltage of 0 2 volts or voltage problem Does TPS 1 voltage ever fall below 0 2 volts Go to Intermittent ON to Step 7 to Step 5 Disconnect the TPS 1 electrical connector Jumper the 5 volt reference circuit pin A and TPS 1 signal circuit pin C together at the throttle connector Key ON Does DST display TPS 1voltage of 4 0 volts or eater epair the Disconnect ECM wire harness connector circuit as Using a DVOM check continuity between TPS 1 Heisse connector signal pin C and ECM connector TPS 1 Refer to A Section 1C2 for wiring repairs epair the terminals for damage corrosion or contamination circuit as Did you find a problem necessary Refer to Wiring Repairs in Engine Electrical oto E Connect any disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine perf
147. ds the operating material conditions at the time the diagnostic fails The The knock sensor head is clear from hoses first time the diagnostic fails the control module brackets and engine electrical wiring DTC P0325 kop jna v jo NE s Schematic Reference Engine Controls Schematics Did you perform the Diagnostic System Check Engine Controls Go to Diagnostic System Check Go to Step 2 Engine Controls Important you can hear an engine knock repair the engine mechanical problem before proceeding with this diagnostic 1 Observe the Freeze Frame and Failure Records data for this DTC 2 2 OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and Failure Records data that you observed Go to Intermittent Did the DTC fail this ignition Go to Step 3 Conditions Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement Go to Step 4 Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass Go to Step 5 Go to Step 2 IMPCO Technologies Engine Service Manual 21 1C7 Ignition System 4 3 liter Emission Certified GM Engine Engine Engine Controls 4 3L DTC P03
148. e Closed Loop Operation Applies to systems utilizing an oxygen sensor In this mode of operation the system uses oxygen sensor information to determine air fuel ratio Adjustments are made accordingly and checked by comparing the new oxygen sen sor to previous signals No stored information is used CNG Compressed Natural Gas CKP Crankshaft Position Sensor CMP Camshaft Position Sensor Conductor A material normally metallic that permits easy passage of electricity Contaminants Impurities or foreign material present in fuel Control Module One of several names for a solid state microcomputer which monitors engine conditions and controls certain engine functions i e air fuel ratio injection and ignition time etc Converter A LPG fuel system component containing varying stages of fuel pressure regulation combined with a vaporizer Cryogen A refrigerant used to obtain very low temperatures Current The directed flow of electrons through a conductor Measured in amps Dedicated Fuel System A motor fuel system designed to operate on only one fuel type Diaphragm A thin flexible membrane that separates two chambers When the pressure in one chamber is lower than in the other chamber the diaphragm will move toward the side with the low pressure Diaphragm Port The external port located at the fuel inlet assembly and connected to the vacuum chamber above the air valve diaphragm Digital Volt Ohm Meter DVOM A meter that
149. e switch is normally open and the fault will set if the switch remains open with the engine running The engine will shut down in the event of this fault to help prevent possible engine damage 34 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 115 Oil Pressure Low se aen Ye No Did you perform the On Board OBD System Check Go to 2 Go to OBD System Check Section Go to Step 3 Repair faulty Oiling System Go to Step 4 Intermittent problem Go to Intermittent section Verify that the engine has oil pressure using a mechanical oil pressure gauge before proceeding with this chart See Engine Specifications Section Does the engine have oil pressure Key On Engine Running DST connected in System Data Mode Clear DTC 115 Warm the engine by idling until the ECT temperature is above 160 degrees F and has been running for at least one minute Increase engine speed above 1300 RPM Does DTC115 reset and cause the engine to shut 5 Replace oil pressure switch Is the replacement complete Key OFF Disconnect ECM harness connector C001 Using a DVOM check for continuity between oil pressure switch connector LT GRN BLK wire and ECM connector pin 37 Do you have continuity between them Go to Step 7 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the Go to Step 8 circuit
150. e Position Throttle Body Sensor Assembly Heat Shield Throttle Body to Manifold Adapter amp FIGURE 3 MIXER AND THROTTLE BODY ASSEMBLY IMPCO Technologies Engine Service Manual 5 1E1 Fuel System Installation Procedure 6 a small amount of O ring lubricant to the PTV o ring before installation Install the TMAP Install and tighten the two 2 retaining bolts Tighten 7 Nem 62 Ib in Start the vehicle THROTTLE BODY REPLACEMENT Fuel Trim Valve Throttle Position Sensor Throttle Cable Connection Foot Pedal Position Throttle Body Sensor Assembly FIGURE 4 THROTTLE BODY ASSEMBLY Removal Procedure 1 13 14 15 6 Disconnect the negative battery cable Remove the air intake duct Disconnect the governor control device electrical con nector Disconnect the throttle cable Disconnect the FTV electrical connector Disconnect Both TPS electrical connectors Disconnect the FTV supply line Disconnect the PTV vacuum line Disconnect the balance line to the LPR Release mixer fuel inlet hose clamp and remove hose from mixer inlet Remove the four 4 manifold to adapter retaining bolts from the throttle body adapter and retain bolts Lift assembly from the adapter and cover the throttle body opening with a clean cloth Remove and discard the adapter o ring Remove the four 4 throttle body to mixer bolts and retain Remove throttle body assembl
151. e adaptive multiplier exceeds the limits of normal operation Diagnostic Aids Always diagnose any other ECM codes that are present before beginning this diagnostic procedure Fuel System High secondary fuel pressure will cause the system to run rich A worn fuel mixer faulty PTV pressure trim valve or FTV fuel trim valve can also cause the system to run rich Fuel Quality A drastic variation in fuel quality very high butane content may cause the system to run rich Be sure that the specified HD 5 or HD 10 motor fuel grade propane is used 114 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 244 Adaptive Learn Low LPG ro _________ Vae Ye Ne e Perform the On Board OBD System Check Go to ET 3 Goto Step 2 Are any other DTCs present Go to Step 7 Go to Step 4 Go to Step 7 Go to step 4 Visually and physically check the following items The air intake duct for being collapsed or restricted The air filter for being plugged ECM grounds for being clean and tight Refer to Section 1C Engine Electrical Power and Ground Distribution Fuel System Diagnostics Refer to Section 1B Fuel System Diagnostics Was a repair made Diagnose any other DTC codes before proceeding with this chart Have any other DTC codes been detected diagnosed and repaired Replace HO2S sensor s the replacement complete System OK Go to OBD System Check
152. e between the See Go to Step 6 Go to step 5 two terminals of the ECT sensor and compare the resistance resistance reading to the chart chart vs Key On Does the DST display ECT voltage of 0 05 volts or Is the resistance value correct temperature in the DTC 121 circuit description 5 e Replace ECT sensor Is the replacement complete Inspect the ECT wire harness connector terminals for damage corrosion or contamination Did you find a problem Repair the Go to Step 7 circuit as necessary Refer to Wiring Repairs in Engine Electrical Key OFF Repair the Intermittent Disconnect ECM wire harness connector circuit as problem Inspect ECM connector pins 31 and 49 for necessary Go to damage corrosion or contamination Refer to Intermittent Did you find a problem Wiring Repairs section in Engine Electrical Jumper the ECT signal pin A at the ECT connector Go to Step 9 Go to Step 12 to engine ground Does DST display ECT voltage of 0 05 or less IMPCO Technologies Engine Service Manual 39 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Go to Step 10 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the Go to Step 11 circuit as necessary Refer to Wiring Repairs in Engine Electrical puku PRESE 13 Go to Step Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Disconnect ECM wire harness
153. e code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 140 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 556 RTI 3 Loss Step values Ye Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code section Does DTC 555 reset with the engine idling e Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine w
154. e ground terminals G1 and G2 clean and tight connector pin C and ECM connector pin 11 Do you have continuity between them e Inspect the connector C009 terminals for damage corrosion or contamination Did you find a problem e Inspect the ECM connector C001 terminals 11 12 and 50 for damage corrosion or contamination Did you find a problem e Replace sensor using R amp R procedure in Section Pay special attention to sensor reluctor wheel inspection Is the replacement complete e Replace ECM e 5 the replacement complete 1 Using a DVOM check for continuity between CKP IMPCO Technologies Engine Service Manual 77 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to Step 9 Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 142 check for any stored codes Does the engine operate normally with no stored codes Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the eng
155. e in an ap proved Gasoline container Turn ignition OFF for 10 seconds Turn ignition ON Is pressure within specified value The fuel return hoses are plugged or restricted lo cate and repair the problem Go to Step 27 Is the action complete Check for restricted engine return pipe Was a problem found Go to Step 27 Go To Step 21 Remove pressure regulator and check for restric tion Go to Step 27 Goto Step 9 Was a problem found 22 Fuel Pressure is within spec but does not hold pressure Go to Step 23 Install J 37287 fuel line shut off adapter or suitable valve to close off fuel supply Make sure valve is open With the ignition OFF Go to Step 24 Go to Step Install a 10 amp fused jumper to the B 25 Pressure should rise Disconnect the jumper and close Did pressure hold Check for leaking fuel pump supply line jeje Was there a problem found IMPCO Technologies Engine Service Manual 5 1B2 LPG Fuel System Diagnostics 6 Open valve in fuel pressure pipe Reconnect test jumper and wait for pressure to build Disconnect jumper and close valve in fuel pressure pipe Does Pressure hold 1 Locate and correct leaking injectors Is the action complete 1 Disconnect all test equipment 2 Install the test port cap 3 Start the engine 4 Verify engine is in closed loop and no MIL is on Is the action complete IMPCO Technologies Engine Service Manual Go to Step 9 G
156. e is cranking or running The ECM will use the default value for the sensor in the event of this fault 24 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 112 IAT VOLTAGE LOW MOTOROLA TMAP Value s Yes mo Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to step 3 Intermittent e KeyOn problem DST Diagnostic Scan Tool connected in Go to System Data Mode section Does DST display IAT voltage of 0 05 or less e Key Off Go to step 4 Go to step 5 e Disconnect the TMAP sensor wire harness connector e Key ON Does the DST display IAT voltage of 4 9 volts or greater 4 Replace TMAP sensor Go to Step 9 Is the replacement complete e Key OFF Repair the Go to step 6 5 e Disconnect ECM wire harness connector circuit as Check for continuity between TMAP sensor necessary connector ground pin A and TMAP sensor Refer to connector signal pin B d Repairs Do you have continuity between them In Engine Electrical Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete uu NEM System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 25 Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds
157. e key on engine off repair it as soon as possible Once the engine is in start or run mode the lamp should go off If the lamp illuminates while the engine is in the start or run mode a current Diagnostic Trouble Code may be set Always use the OBD System Check chart on the next page of this manual to verify proper MIL operation before proceeding with a DTC diagnostic code repair 12 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 Step Key ON ngine Does the MIL illuminate tart the engine Does the MIL lamp turn off ey ON engine O Check for voltage between MIL power source and engine ground Do you have voltage Replace MIL lamp Did that solve the problem Disconnect ECM wire harness connector C001 Using a DVOM check for continuity between MIL ground and ECM terminal 26 nave CONUNU nspect the Replace ECM Is te replacement complete Back probe the M connector C022 Using a DVOM check for continuity through connector C022 Do you have continuity nspect the M Active DTC Diagnostic trouble code is stored in memory Proceed with DTC diagnosis If no active DTC is OBD System Check amp socket connector and ECM terminal 26 for damage corrosion or contamination Did you find a problem amp socket connector and ECM terminal 26 for damage corrosion or contamination Did you find a problem properly OBD E Check Repai
158. e pressure drop by the specified value Go to Step 8 Go to Step 9 1 Locate and repair loss of vacuum to the pres sure regulator Is the action complete Replace pressure E Is the action complete Is pressure less then specified value 285 325 kPa 41 47 psi Go to Step 14 Go to Step 11 1 With the fuel pressure gage installed 2 Start engine and accelerate with load 285 325 kPa Is pressure less then specified value 41 47 psi Go to Step 12 Go to Step 14 1 Check for restricted fuel filter 2 Check for restricted fuel supply line from pump Was a problem found Go to Step 27 Go to Step 13 1 Replace fuel pump Is this action Complete Go to Step 27 With the ignition OFF 1 Install a 10 amp fused jumper to the B 2 Slowly pinch the fuel return line 325 kPa 47 3 Pressure should rise psi Go to Step 9 Go to Step 15 NOTE Do not exceed 414 kPa 60 psi Did Pressure rise 4 IMPCO Technologies Engine Service Manual Check for restricted fuel pump strainer Check for leaking fuel supply line from pump Check to ensure fuel pump is correct Was a problem found Go to Step 27 Goto Step 16 Is this action Complete Go to Step 27 Is pressure greater then specified value 285 325 kPa 41 47 psi Go to Step 15 Disconnect the fuel return hose at the fuel rail Attach a length of hose to the return pipe at 285 325 kPa the rail 41 47 psi Goto Step 19 Go to Step 20 Place the other end of the hos
159. e replace 4 3 liter Emission Certified GM Engine Maintenance OB e Check for coolant leaks at the radiator tank seams Do not remove the cooling system pressure cap when the engine is hot Allow the engine to cool and then re move the cap slowly allowing pressure to vent Hot coolant under pressure may discharge violently and inlet joints repair or replace as necessary e Check for leaks at the radiator hose connections tighten hose clamps if necessary e Check Radiator hoses for swelling separation cracks deterioration in the hoses or hardening if any of these conditions exist the hose should be replaced with the OEM replacement parts e Check coolant level if low add with 50 50 mixture Do not add plain water e Replace coolant per the recommended schedule at the end of this section Checking the Coolant Level 1 Check coolant level in coolant recovery tank Add specified coolant as required IMPORTANT The engine manufacturer and the fuel system supplier do not recommend the use of stop leak additives to repair leaks in the cooling system If leaks are present the radiator should be removed and repaired If the radiator requires repair insure that the radiator core repairs did not result in a significant reduction in the cooling capacity of the radiator The engine manufacturer recommends the cooling system be filled with a 50 50 mixture of ethelyene glychol anitfreeze and water This GM industri
160. e run throught the sheet metal FUEL FILTER Propane fuel like all other motor fuels is subject to contami nation from outside sources Refueling of the equipments tank and removal of the tank from the eguipment can inad vertently introduce dirt and other foreign matter into the fuel system It is therefore necessary to filter the fuel prior to entering the fuel system components down stream of the tank An inline fuel filter has been installed in the fuel system to remove the dirt and foreign matter from the fuel The inline filter is replaceable as a unit only Maintenance of the filter is critical to proper operation of the fuel system and should be replaced as defined in the Maintenance Schedule SECTION OB In severe operating condition more freguent replacement of the filter may be necessary Fuel Flow 1473 Figure 3 Inline Fuel Filter ELECTRIC LOCK OFF The Electric Lock Off device is an integrated assembly The electric lock assembly is a 12 volt normally closed valve The solenoid is mounted to the valve body When energized the solenoid opens the valve and allows the Propane fuel to flow through the device The valve opens during cranking and run IMPCO Technologies Engine Service Manual 3 1A1 Fuel System Operation 4 3 liter Emission Certified GM Engine cycles ofthe engine The lock off supply voltage is controlled by the engine control module ECM Figure 4 Electric Fuel Lock Off
161. e sole noid plunger to protect them from exposure to dirt icing conditions and splash LUBRICATION Starter motors do not reguire lubrication except during overhaul SOLENOID REPLACEMENT When a no crank and no sound starter conditions exists check solenoid before disassembling starter Solenoid can be checked without removal Refer to Cleaning Inspection and Testing in this Section Solenoid can be serviced separately from the drive and housing Refer to Starter Motor Disassembly and Starter Motor Assembly in this Section STARTER REPLACEMENT Remove or Disconnect 1 Negative battery cable Bolts to flywheel inspection cover Starter wiring Flywheel inspection cover Starter mounting bolts 6 Starter Install or Connect 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine NOTICE Before installing starter motor to engine tighten inner nuts on solenoid terminals to be sure they are secure in cap Tighten inner nuts on battery terminal and motor terminal to 10 Nem 88 Ib in If nuts are not properly tightened starter may fail later due to terminal or cap damage 1 Starter 2 Starter mounting bolts Tighten Bolts to 30 22 Ib ft 3 Starter wiring Tighten Nut on solenoid battery terminal to 8 71 Ib in Nut on S terminal to Nem 26 Ib in 4 Flywheel inspection cover Tighten Bolts to 7 Nem 62 Ib in 5 Negat
162. e vacuum leak Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 651 check for any stored codes Does the engine operate normally with no stored codes 7 e Correct mechanical operation of the throttle Refer Go to step 9 to Engine amp Component R amp R Section 1E Has the mechanical operation of the throttle been corrected 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine imit DTC 652 Fuel Rev Conditions for Setting the DTC 166 Fuel Rev Limit Adaptive Enabled PNK WHT TAN ORN PPL LT BLU BLK LT GRN LT GRN RED Check Condition Engine Running Fault Condition Engine RPM greater than 4000 for 2 seconds continuously MIL On during active fault Closed Loop Enabled TPS 1 Signal Sensor Ground FPP Signal 5 VOLTS ECM Circuit Description This fault will set anytime engine RPM exceeds 4000 for 2 seconds or more continuously When these conditions are met the ECM shuts off the fuel injectors This is to help prevent engine or equipment damage The MIL will be on during this active fault IMPCO Technologies Engine Service Ma
163. ect the condition 1 Check for a faulty connection at the powertrain control module PCM 2 Repair the connector as necessary Refer to Connector Repairs in Wiring Systems Did you find and correct the condition Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement 1 Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass Replace the CKP sensor or the crankshaft reluctor wheel Refer to Crankshaft Position CKP Sensor Replacement or Crankshaft Position CKP Reluctor Ring Replacement in Engine Mechanical Did you complete the replacement Go to Step 15 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 Crankshaft Sensor Replacement Removal Procedure 1 Disconnect the sensor harness connector 10937 2 Remove the CKP sensor mounting bolt 10938 3 Remove the CKP sensor 44496 IMPCO Technologies Engine Service Manual 27 1C7 Ignition System 4 3 liter Emission Certified GM Engine 28 IMPCO Technologies Engine Service Manual 1n027 Installation Procedure Important When installing the CKP sensor make sure the sensor is fully seated before tightening the mounting bolt A poorly seated CKP sensor may perform erra
164. ections in Wiring Systems Did you find and correct the condition Go to Step 11 Go to Step 10 Replace the KS Refer to Knock Sensor KS Replacement Did you complete the replacement Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the diagnostic test run and pass Go to Step 12 Go to Step 2 With a scan tool observe the stored information Capture Info Go to Diagnostic we Does the scan tool display any DTCs that you have not Trouble diagnosed Code DTC List System OK 24 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0335 SIE ID 693518 Circuit Description stores this information in the Failure Records If The crankshaft position CKP sensor signal indicates the diagnostic reports a failure on the second consecutive ignition cycle the control module records the operating conditions at the time of the failure The control module writes the operating conditions to the Freeze Frame and updates the Failure Records SIO ID 727824 Conditions for Clearing the MIL DTC the crankshaft speed and position The CKP sensor is connected directly to the powertrain control module PCM and c
165. ed Loop multiplier and the adaptive multiplier This fault sets ifthe Closed Loop multiplier exceeds the limits of normal operation When the multiplier cannot correctly modify the fuel flow within its limits it is limited at 35 Diagnostic Aids Always diagnose any other ECM codes that are present before beginning this diagnostic procedure Fuel System The system will be rich if an injector fails in an open manner High fuel pressure due to a faulty fuel regulator or obstructed fuel return line will cause the system to run rich Ignition noise open or poor ground circuit to or in the ignition system or ECM may cause EMI Electromagnetic interference This noise could be interpreted by the ECM as ignition pulses and the sensed RPM becomes higher than the actual speed The ECM then delivers too much fuel causing the system to run rich TMAP Sensor A higher manifold pressure than normal can cause the system to go rich Temporarily disconnecting the MAP Sensor will allow the ECM to set a default value for MAP IAT Sensor Check for a shifted sensor that could cause the ECM to sense lower than actual temperature of incoming air This can cause a rich exhaust condition ECT Sensor Check for a skewed sensor that could cause the ECM to sense engine temperature colder than it actually is This could also cause a rich exhaust condition 100 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4
166. efer to Wiring Repairs in Engine Electrical o to System Check Section problem Go to Intermittent epair the circuit as necessary Refer to Wiring Repairs in Engine Electrical to Step 7 problem Go to Intermittent section IMPCO Technologies Engine Service Manual 143 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine sensor connector ground circuit pin B 4 with a test light connected to battery voltage Does the test light come on e Disconnect ECM wire harness connector circuit as e Inspect the ECM wire harness connector necessary terminals for damage corrosion or contamination Refer to Did you find a problem wining in Engine o to Step 10 Repair the Disconnect ECM connector circuit as Check continuity between FPP sensor connector necessary ground pin B and ECM connector FPP sensor Refer to ground pin 49 Wiring Repairs Do have continuity between them E cus emove all test equipment except the 051 ystem OK Connect disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 611 check for any stored codes Does the engine operate normally with no sto
167. el hose connection between the LPR and the mixer assembly for damage or leakage Was a problem found and repaired Go to Step 26 Goto Step 12 1 Connect a 0 10 psi gauge to the primary test port of the low pressure regulator LPR 2 Crankthe engine and observe the pressure 2 0 4 0 psi reading for the LPR primary pressure Is the fuel pressure ABOVE the specified value Go to Step 22 Go to Step 13 Turn OFF the ignition Disconnect the LPL connector Install a test light between the pins of the LPL connector Crank the engine The test light should illumi nate Go to Step 14 Go to Step 16 Does the test light illuminate Using a DVOM check the resistance of the low pressure lock off LPL Is the resistance within the specified range Go to Step 15 Goto Step 23 1 Turn the ignition OFF 2 Close the manual shut off valve on the LPG tank CAUTION When disconnecting LPG fuel lines liq uid LPG may be present Perform this step in a well ventilated area 3 Loosen the fuel inlet hose fitting at the inlet of the LPL Was fuel present when the fitting was loosened era See sep i 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine LPG Fuel System Diagnostics 1B1 Go to Step 20 Go to Step 21 Go to Step 19 Go to Step 23 Go to Step 26 Go to Step 26 Go to Step 26 m Turn OFF the ignition Connect the test light to chassis ground and probe pin A ofthe LPL connector Cr
168. el select voltage 104 volts Spark kill Nomal Closedloop 1 Imi Fuel pump voltage 138 vols Injector kill Normal V Adaptive 1 oo z Gov voltage 206 vols Of v se mue Gov2 voltage 206 vols A Overspeed voltage 59 volts Flight Data SnapShot SnapShot Closedloop 2 ox i Base Base Custom To z B0 vota Definitions Definitions Definitions em ma O Pv Historic Faults Active Faults FPP pet em EMPTY Double click faul for information Double click fault for information pct IMAP EMPTY 0 voltage low 88 voltage high E JAT voltage high 08 voltage high usw EMPTY em o A BM2 A BM2 Ma Flight Data FPP Pet Custom TPS_pet Definitions ves EMPTY EGO2 volts ___ HM hours The System Fault screen is used to view and clear DTC s which have been set Checking Diagnostic Trouble Codes The System Fault screen contains a listing of all of the Historic and Active set within the system If a D TC is stored in memory the screen will display that fault in the History column If the fault is active it will also show up in that column Clearing Diagnostic Trouble Codes To clear a DTC from memory use the arrow keys or mouse to move the Press the Enter key to clear the fault from memory NOTE Record faults before erasing them for reference during
169. el trim valves and ignition coils This fault will set if the ECM detects system voltage less than 9 0 for 5 seconds or longer while the alternator should be charging The adaptive learn is disabled 116 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 261 System Voltage Low Value s Yes mo Did you perform the On Board OBD System Check Go to ET 2 Go to OBD System Check Section Intermittent Go to Step 3 problem Go to Engine Electrical Intermittent section Go to Step 4 Replace Battery Go to Step 5 Repair charging System na n probe ECM connector pins 22 and 23 Repair ECM Go to Step 6 Measure voltage with DVOM between each pin Ground circuit and engine ground Go to Power Is the voltage greater than 9 0 volts and Ground section in engine Electrical Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Does DST display system voltage greater than 9 0 Check a condition a it OK Recs oo system Repair ECM Go to step 7 power circuit Go to Power and Ground section in engine Electrical Back probe ECM connector pins 19 and 20 Measure voltage with DVOM between each pin and battery voltage Is the voltage greater than 9 0 volts System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 117 Remove all test except the DST Connect any disconnected components fuses
170. ely mounted Check filter housing for external damage or distortion if damaged replace fuel filter To replace the filter use the following steps 1 Move the equipment to a well ventilated area and insure all external ignition sources are not present 2 Start the engine 3 With the engine running close the manual valve 4 When the engine runs out of fuel turn OFF the key when the engine stops and disconnect the battery negative cable IMPORTANT A small amount of fuel may still be present in the fuel line use gloves to prevent burns wear proper eye protection If liquid fuels continues to flow from the connections when loosened check to make sure the manual valve is fully closed 5 Slowly loosen the inlet fitting and disconnect 6 Slowly loosen the outlet fitting and disconnect 7 Remove the filter housing form the equipment 8 Check for contamination 9 the opening of the filter on a clean cloth 10 Check for debris 11 Check canister for proper mounting direction 12 Reinstall the filter housing to the equipment 13 Tighten the inlet and outlet fittings to specification 14 Open the manual valve 6 IMPCO Technologies Engine Service Manual IMPORTANT The fuel cylinder manual valve contains an Excess Flow Check Valve open the manual valve slowly to prevent activating the Excess Flow Check Valve 15 Check for leaks at the inlet and outlet fittings and the filter housing end connection usi
171. em 1C7 516428 Legend 1 Propshaft Speed Sensor Rear Connector 4 Propshaft Speed Sensor Front Connector 2 Transfer Case Encoder Motor Connector 5 Transfer Case 3 Vehicle Speed Sensor VSS Connector 6 P301 IMPCO Technologies Engine Service Manual 5 1C7 Ignition System 4 3 liter Emission Certified GM Engine J DTC P0140 cont d Remove the jumper from the previous step Is the ENG 1 fuse open 1 Turn ON the ignition with the engine OFF 2 Probe the HO2S ignition 1 voltage circuit with a test lamp that is connected to a good ground Does the test lamp illuminate Connect a test lamp between the affected HO2S ignition 1 voltage circuit and the HO2S heater ground circuit 2 Turn ON the ignition with the engine OFF Does the test lamp illuminate Disconnect all HO2S pigtail connectors Test HO2S ignition 1 voltage circuit for a short to ground Refer to Circuit Testing and Wiring Repairs in Wiring Systems Replace the ENG 1 fuse Did you find and correct a short to ground in the ignition 1 voltage circuit Important Perform the following test on HO2S bank 1 sensor 1 HO2S bank 2 sensor 1 and HO2S bank 1 sensor 2 A condition in any sensor will cause this DTC to set Test the HO2S ignition 1 voltage circuit sensor side for a short to the HO2S body Refer to Circuit Testing in Wiring Systems Did you find the condition Important Perform the following test on HO2S ba
172. emoving lift each brush spring and rest against side of brush this prevents brush damage when assembly is pulled off of commutator If springs are allowed to push brushes down when brush is moved off of commutator the brush pigtail lead may be separated from the brush 8 Slightly separate gear and drive assembly from drive end frame and use screwdriver to pry plastic shift lever off drive pins 9 Gear and drive from drive end frame 10 Thrust collar from armature shaft then slide deep socket over shaft tap socket to drive pinion stop collar off retainer ring 11 Retainer ring and drive from shaft IMPCO Technologies Engine Service Manual 3 1 828 4 3 litINEVS RME ENGINE FRAME AND FIELD SCREW BRUSH HOLDER DRIVE ASSEMBLY TUBE DRAIN ATTACHMENT 2 REQUIRED NUT FIELD LEAD TO ARMATURE THRU BOLT 2 REQUIRED SOLENOID SPRING BRUSH SHIELD AND GEAR ASSEMBLY BEARING BRUSH HOLDER ASSEMBLY SHAFT AND GEAR ASSEMBLY HOUSING DRIVE END BALL BEARING GEAR AND BEARING COLLAR THRUST FRAME COMMUTATOR END ASSEMBLY RING PINION STOP BEARING ROLLER INTERNAL COLLAR PINION STOP TOOTH NOOPWN gt SAW BLADE VOLTMETER CARBON PILE BATTERY GROWLER ANN_NAL 600 036 Figure 4 17 Testing Armature for Short Circuits Figure 4 18 Testing Solenoid Windings inanan n m A a 4 4 4 gt IES 131 8 98 statig Siepen Certified GM Engine 165 CLEANING INSPE
173. en brushes are excessively worn when compared to a new brush they should be replaced Make sure the brush holders are clean and the brushes are not binding in the holders The full brush surface should ride on the commutator to give proper performance Check to insure that brush springs are giving firm contact between the brushes and commutator When the springs are distorted or discolored they should be replaced When test eguipment is available Check the armature for short circuits by placing on growler and holding hack saw blade over armature core while armature is rotated figure 4 17 If saw blade vibrates IES 131 8 98 on the armature core or shaft If the lamp lights the armature is grounded and must be repaired or replaced 7 Check solenoid windings To check hold in winding connect an ammeter and switch in series with a 12 volt battery and the switch terminal on the solenoid Connect a voltmeter to the S terminal and to ground Connect carbon pile across battery Adust the voltage to 10 volts and note the ammeter reading Refer to figure 4 18 PG260 starter motor reading should be 10 to 20 amperes To check both windings connect as for previous test Ground the solenoid motor terminal S Adjust the voltage to 10 Volts and note the ammeter reading It should be 60 to 85 amperes for PG260 motors LUBRICATED GEAR TEETH PLANETARY GEAR AND SHAFT ASSEMBLY 131 158 131 158 Figure 4 1
174. ent and Poor Connections and Repairing Connector Terminals in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 13 Repair the ignition 1 voltage supply circuit of the fuel injector for an open or for a short to ground Refer to Wiring Repairs in Wiring Systems Did you complete the repair Go to Step 14 Replace the fuel injector Refer to Fuel Injector Replacement Did you complete the replacement Go to Step 14 Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass Go to Step 15 Go to Step2 With a scan tool observe the stored information Capture Info Go to Diagnostic Does the scan tool display any DTCs that you have not diagnosed Trouble Code DTC List System OK 14 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0230 SIE ID 789976 Circuit Description The powertrain control module PCM provides ignition positive voltage to the coil side of the fuel pump relay When the ignition switch is first turned ON the PCM energizes the fuel pump relay which applies power to the fuel pump The PCM enables the fuel pump rel
175. ep 4 Is the PTV duty cycle within the specified range Go to Step Go to Step 5 5 Is the PTV duty cycle ABOVE the specified value 8096 Go to Step 7 Go to Step 1 Raise the engine speed to approximately 2500 RPM or greater ER 2 Observe the duty cycle reading of the PTV en Is the PTV duty cycle withing the specifed range Go to Step f Go to Step IMPCO Technologies Engine Service Manual 7 1B1 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine 7 1 Connect the Diagnostic Scan tool 2 Start the engine and allow it to reach oper ating temperature 3 With the engine idling observe the duty cycle reading of the FTV on the scan tool OR Back probe the FTV connector Contect a duty cycle monitoring tool at connector as follows IMPCO FSA Yellow clip ot pin B 20 80 Green Clip not used for this test Red clip to 12V battery positive Black Clip battery negative DVOM Back probe the FTV connector Set the DVOM for duty cycle percentage and connect between pin B and battery negative Is the FTV duty cycle within the specifed range Go to Step 24 Go to Step Is the FTV duty cycle ABOVE the specified value 80 ________ Goto Step Go to Step 1 Connect the negative lead of the DVOM to a know good engine ground 2 Using the positive lead of the DVOM Back probe Pin B at the PTV connector 12 6 V to 15 1 V Was the PTV voltage within the specified range Go to Step 12 Go to Step 10 1 10 1
176. eports a failure on the ond consecutive ignition cycle the control Jule records the operating conditions at time of the failure The control module writes operating conditions to the Freeze Frame updates the Failure Records 7824 ions for Clearing the MIL DTC control module turns OFF the malfunction cator lamp MIL after 3 consecutive ignition les that the diagnostic runs and does not fail urrent DTC Last Test Failed clears when the jnostic runs and passes 4 3 liter Emission Certified GM En ine Ignition System 1C7 A history DTC clears after 40 consecutive warm up cycles if no failures are reported by this or any other emission related diagnostic Clear the MIL and the DTC with a scan tool Diagnostic Aids The misfire index counts the number of misfires The scan tool can monitor the misfire index There is a current and a history misfire counter for each cylinder Use the current misfire counter in order to determine which cylinder is misfiring Use the history misfire counter for misfires that are not currently present Many different conditions could cause an intermittent misfire Inspect the following conditions Inspect the ignition control IC circuit for an intermittent short to ground Ensure that the spark plug wires are securely attached to the spark plugs and the distributor cap Ensure that the coil wire is securely attached to the distributor cap and the coil Inspect the wire routing t
177. equivalent that spark plugs are correct for use with LPG R42LTS Check the spark plugs for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Check for bare or shorted ignition wires Check for moisture in the distributor cap if applicable Check for loose ignition coil connections Important 1 Ifthe engine starts but then immediately stalls check Crankshaft Position CKP sensor 2 Check for improper gap debris or faulty connections 6 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Engine Mechanical Checks Exhaust System Checks Important The LPG Fuel system works on a fumigation principle of fuel introduction and is more sensitive to intake manifold leakage than the gasoline fuel supply system e Check for the following Vacuum leaks Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes Ref Check the intake and exhaust manifolds for casting flash Check the exhaust system for a possible restriction Inspect the exhaust system for damaged or collapsed pipes Inspect the muffler for signs of heat distress or for possible internal failure Check for possible plugged catalytic converter Refer to Restricted Exhaust System Diagnosis IMPCO Technologies Engine Service Manual 7 1B4 System Diagnostics 4 3 liter Emission
178. es the engine operate normally with no stored codes 106 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 107 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 242 Adaptive Rich Fault low limit gasoline DK GRN ORN HO2S i E A 49 Sensor Ground Heater C PNK DK GRN To System Power Relay ToEngine Ground Conditions for Setting the DTC Heated Oxygen Sensor Functional Fault Adaptive multiplier out of range at limit of 30 MIL On during active adaptive limit condition Adaptive Enabled Closed Loop Enabled Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the Adaptive multiplier This fault sets if the Adaptive multiplier exceeds the limits of normal operation Diagnostic Aids Always diagnose any other ECM codes that are present before beginning this diagnostic procedure Fuel System The system will be rich if an injector fails in an open manner High fuel pressure due to a faulty fuel regulator or obstructed fuel return line will cause the system to run rich Ignition noise open or poor ground circuit to or in the ignition system or ECM may cause EMI Electromagnetic in
179. ese terminals cannot be straightened once they are bent Make certain that the connectors are properly seated and all of the sealing rings in place when connecting leads The hinge type flap provides a backup or secondary locking fea ture for the connector They are used to improve the connec tor reliability by retaining the terminals if the small terminal lock tangs are not positioned properly Weather Pack connections cannot be replaced with standard connections Instructions are provided with Weather Pack connector and terminal packages 4 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 5 6 4 3L MAIN HARNESS coo1 ECM 18 ORANGE BLUE 16 NIE INI 2 S 2 DKRUETE AT m 3 VELLOW GRAY 18 EE oxsuereuows FEN 36 DK BLUE YELLOW18 power rouno Lae ae POWER GROUND Dr m SVOLTREF Pepe L ramo VSW i en NK 2 KNK CRANK CRANK CAM CAM VBAT VBAT STARTER LOCKOUT FUEL LOCKOFF FUEL PUMP2 RELAY CONTROL 51 TPS2 DBW OIL PRESSURE TACH MIL AUX ANA PD2 AUXOUTIA FUELSELECT AUX ANA PU2 GOV SELECT GASEOUS TRIM CAN CAN RS232TX RS232 RX COLI a INS 6 NJ AUXOUT3 i1 PURPLE WHITE 18 12 WHITE PURPLE 18 T3 GRAY BROWN 18 PURPLE ORANGE 22 RED TAN 16 23 RED TAN 16 5 GRAY ORANGE TS B_WHITE BLACK 18 3 TAN BLACKIE 10 WHITEA
180. est light connected to battery voltage e Key ON Does DST display TPS 1 voltage less than 0 2 volts connector signal terminal and engine ground Go to OBD System Check Go to Step 2 Section Go to Step 3 Intermittent problem Go to Intermittent section B Go to Step 6 Go to Step 4 Repair the Go to Step 5 circuit as necessary Refer to Wiring Repairs in Engine Electrical Replace ECM Go to Step lt MAH Is the replacement complete e Back probe sensor ground circuit at ECM connector with test light connected to battery voltage Does the test light come on Key OFF Disconnect ECM wire harness connector Using a DVOM check for continuity between throttle connector signal ground and ECM signal ground circuit terminals Do you have continuity between them 4 Key OFF Disconnect ECM wire harness connector Key ON Using a DVOM check for voltage between throttle Do you have voltage m Go to Step 9 Goto NN 7 Repair the circuit as necessary Go to Step 8 Refer to Section 1C2 for wiring repairs e Replace ECM Go to Step 13 e 5 the replacement complete e Check throttle for foreign object in bore Go to Step 10 Go to Step 11 Did you find a foreign object in the bore 10 Remove foreign object Go to Step 13 Is the removal complete e Inspect the throttle wire harness connector Repair the Go to Step 12 terminals for damage corrosion or contamination circuit as Did you find the p
181. f severe enough the engine or vehicle may shake The engine idle speed may vary in RPM Either condition may be severe enough to stall the engine Sensor Checks e Check for silicon contamination from fuel or improperly used sealant The sensor will have a white powdery coating The sensor will result in a high but false signal voltage rich exhaust indication The ECM will reduce the amount of fuel delivered to the engine causing a severe driveability problem Check the Heated Exhaust Gas Oxygen Sensor HEGO performance Check the Temperature Manifold Absolute Pressure TMAP sensor response and accuracy Fuel System Checks Check for rich or lean symptom that causes the condition Drive the vehicle at the speed of the complaint Monitoring the oxygen sensors will help identify the problem Check for a sticking mixer air valve Verify proper operation of the Injectors Perform a cylinder compression test Refer to Engine Mechanical in the Service Manual Check the fuel Rail pressure Refer to the Gasoline Fuel System Diagnosis Check injector electrical connections Ignition System Checks Check for the proper ignition output voltage using the spark tester J26792 or the equivalent Verify that the spark plugs are correct use R42LTS Check the spark plugs Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Blistered insulators Heavy deposits Check the sp
182. fer to Wiring Repairs in Engine Electrical o to step 7 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical un NE ystem OK OBD System Check IMPCO Technologies Engine Service Manual 23 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 112 IAT Low Voltage Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Cranking or Running Fault Condition IAT Sensor Voltage less than 0 05 MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled and allowed to stay at limit if required but will then also set the limiting fault Circuit Description The TMAP is a combined Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunetion with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The is a calculated value based mainly on the sensor at high airflow and influenced more by the Engine Coolant Temperature at low airflow This fault will set if the signal voltage is less than 0 05 volts anytime the engin
183. ful to your health avoid skin contact 3 Remove drain plug and allow the oil to drain 4 Remove and discard oil filter and it sealing ring 5 Coat sealing ring on the new filter with clean engine oil wipe the sealing surface on the filter mounting surface to remove any dust dirt or debris Tighten filter securely follow filter manufacturers instructions Do not over tighten 6 Check sealing ring on drain plug for any damage replace if necessary wipe plug with clean rag wipe pan sealing surface with clean rag and re install plug into the pan Tighten to specification 7 Fill crankcase with oil 8 Start engine and check for oil leaks 9 Dispose of oil and filter in a safe manner FUEL SYSTEM INSPECTION AND MAINTENANCE PROPANE FUEL SYSTEM The Propane fuel system installed on this industrial engine has been designed to meet the emission standard applicable for this equipment for 2004 model year To ensure compli ance to these standards follow the recommended maintenance schedule contained in this section INSPECTION AND MAINTENANCE OF THE FUEL STORAGE CYLINDER The fuel storage cylinder should be inspected daily or at the beginning of each operational shift for any leaks external damage adequate fuel supply and to insure the manual ser vice valve is open Fuel storage cylinders should always be securely mounted inspect the securing straps or retaining devices for damage insure that all locking devices are close
184. g position where it will remain until battery is disconnected 4 Push pinion back toward commutator end to eliminate slack figure 4 11 5 Use feeler gages to check clearance IMPCO Technologies Engine Service Manual 7 168385artne FIELD COIL Disconnect between end of pinion and pinion stop retainer Clearance should be 0 25 to 4 06 mm 0 010 to 0 160 in negative ground lead from motor housing drive pinion will retract into drive end housing then disconnect positive lead from S terminal When clearance is outside specifications recheck motor for proper assembly and for worn or damaged parts in shift mechanism and drive assembly Replace worn parts ATTACHING 777 22664 017 Figure 4 12 Field Coil to Solenoid Strap Removal TAARNA TO 0 F Be E N NE nn 4 3 lite ios ierA Ear NN SYS FEES CONTINUITY METER BATTERY Figure 4 13 Testing Standard Solenoid Four Connection Type IES 131 8 98 4 3 liter Emission Certified GM Engine Starter 1C5 STARTER MOTOR INSTALLATION SOLENOID SWITCH INSTALLATION 1 Place starter motor and solenoid assembly 1 Place plunger spring over plunger Install in position and install attaching nuts Torgue solenoid onto plunger to specifications 2 Twist solenoid to engage lock tab 2 Fasten wires as outlined in wiring diagram 3 Install attaching screws and tighten secure ly SOLENOID REMOVAL T 4 Install field coil connecto
185. g capability These features enhance the ability to diagnose and repair possible problems with the system The graphing feature allows sensor inputs and select control output variables to be plotted in real time while the engine is running To plot a variable you must first TAG the variable you wish to plot To do this use the mouse to highlight the variable and then right click Next press the key or double click the Plot Log button to invoke the plotting feature You may change the desired time interval for each display sereen The default is 10 seconds This can be increased or decreased as necessary to display the desired results You can also change the sample rate You are now ready to plot Simply click the START button to observe the plotted variables The plot sweeps across the screen from left to right To pause the display screen press the SPACE BAR at any time during plotting To continue plotting simply press the SPACE BAR again To stop the plotting feature simply click the STOP button To exit the plotting screen click the CLOSE button The range of each variable is listed along the left side of the display and the time is listed along the bottom of the screen IMPCO Technologies Engine Service Manual 7 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine IGNITION SYSTEM TEST EDIS ECI Serial Commun
186. gnition wires for arcing cross firing and proper routing Ignition coils for cracks or carbon tracking Engine Mechanical Checks Perform a cylinder compression check Check the engine for the following Improper valve timing Bent pushrods Worn rocker arms Worn camshaft lobes Broken or weak valve springs Check the intake and exhaust manifold passages for casting flash Fuel System Checks Check the fuel system plugged fuel filter low fuel pressure etc Refer to Gasoline Fuel System Diagnosis Check the condition of the wiring to the fuel pump and injectors Additional Check Check for Electromagnetic Interference EMI EMI on the reference circuit can cause a missing condition Monitoring the engine RPM with a scan tool can detect an EMI A sudden increase in the RPM with little change in the actual engine RPM indicates EMI is present If the problem exists check the routing of the secondary wires and the ground circuit 22 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Hesitation Sag Stumble DEFINITION The vehicle has a momentary lack of response when depressing the accelerator The condition can occur at any vehicle speed The condition may cause the engine to stall if it s severe enough Preliminary Checks Refer to Important Preliminary Checks Fuel System Checks Ignition System Checks Additional Check Check for fuel pump electrical circuit
187. he following conditions Faulty fuse or circuit breaker Connectors poorly mated Terminals not fully seated in the connector backed out Terminals not properly formed or damaged Terminal to wires poorly connected Terminal tension insufficient Carefully remove all the connector terminals in the problem circuit in order to ensure the proper contact tension If necessary replace all the connector terminals in the problem circuit in order to ensure the proper contact tension Checking for poor terminal to wire connections requires removing the terminal from the connector body Operational Test If a visual and physical check does not locate the cause of the problem drive the vehicle with a scan tool When the problem occurs an abnormal voltage or scan reading indicates the problem may be in that circuit Intermittent Malfunction Indicator The following components can cause intermittent MIL and DTC s Lamp MIL e defective relay Control Module driven solenoid or a switch that can cause electrical system interference Normally the problem will occur when the faulty component is operating The improper installation of electrical devices such as lights 2 way radios electric motors etc The ignition secondary voltage shorted to a ground The Malfunction Indicator Lamp MIL circuit or the Diagnostic Test Terminal intermittently shorted to ground The Control Module grounds Loss of DTC Memory To check for the loss of
188. he gasoline fuel storage tank location may very on equip ment applications The fuel tank may be integrated into the chassis frame or may be a stand alone vessel mounted on the equipment For precise location for the equipment application refer to the OEMs vehicle manual GASOLINE FUEL PUMP The Gasoline is stored as a liquid in the fuel tank and is drawn into the fuel system by a 12 volt electric fuel pump Depending on the vehicle application the fuel pump may be mounted in the fuel tank or as a stand alone component In either case the fuel pump will receive a signal from the ECM at Key On to prime the fuel system for approximately 2 sec onds prior to start Priming of the fuel system provides for a quicker start when the engine begins to crank The fuel pump is an emissions con trol component If the fuel pump fails to operate replace only with an OEM replacement part The fuel pump is calibrated to supply the correct amount of fuel to the injectors Replacing the pump with anything other than the OEM replacement could cause dam age to the fuel system and or damage to the fuel tank FUEL FILTER After the fuel is drawn into the fuel pump the fuel then flows through the gasoline fuel filter The fuel filter will trap small particles as the fuel passes through the filter to remove debris and prevent injectors from becoming damaged Maintenance of the fuel filter is required as indicated in the Recommended Maintenance Schedule
189. he manual shut off valve MSV on the propane fuel tank 2 Start and run the vehicle until the engine stalls 3 Turn the ignition switch OFF IMPORTANT e Residual vapor pressure will be present in the fuel system Ensure the work area is well ventilated be fore disconnecting any fuel line PROPANE FUEL SYSTEM LEAK TEST NEVER USE AN OPEN FLAME OF ANY TYPE TO CHECK FOR PROPANE FUEL SYSTEM LEAKS Always inspect the propane fuel system for leaks after per forming service Check for leaks at the fittings of the serviced or replaced component Use a commercially available liguid leak detector or an electronic leak detector When using both methods use the electronic leak detector first to avoid con tamination by the liguid leak detector 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine PROPANE FUEL FILTER REPLACEMENT FIGURE 1 Fuel Flow 5 FIGURE 1 INLINE FUEL FILTER Removal Procedure 1 Relieve the propane fuel system pressure Refer to Propane Fuel System Pressure Relief 2 Disconnect the negative battery cable 3 Slowly loosen the fuel inlet fitting to the filter and re move the line 4 Remove the outlet fitting from the filter 5 Remove the filter from the retaining bracket and discard Installation Procedure IMPORTANT e sure to install the filter in the correct direction of the flow marked with an arrow e Do Not
190. he plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits e Check the ignition wires for the following items Cracking Hardness Proper connections Cooling System Checks e Checkthe engine thermostat for always being open or for the wrong heat range Additional Check Checkthe transmission shift pattern Refer to the OEM Transmission Controls section the Service Manual e Check for dragging brakes 12 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Rough Unstable or Incorrect Idle Stalling DEFINITION The engine runs unevenly at idle If severe enough the engine or vehicle may shake The engine idle speed may vary in RPM Either condition may be severe enough to stall the engine Preliminary Check e Refer to Important Preliminary Checks Sensor Checks Check for silicon contamination from fuel or improperly used sealant The sensor will have a white powdery coating The sensor will result in a high but false signal voltage rich exhaust indication The ECM will reduce the amount of fuel delivered to the engine causing a severe driveability problem Check the Heated Exhaust Gas Oxygen Sensor HEGO performance Check the Temperature Manifold Absolute Pressure TMAP sensor response and accuracy Fuel System Checks Check for rich or lean symptom that causes the condition Drive the
191. he system will also be lean if an injector fails in a closed manner or is dirty Fuel Pressure Low fuel pressure faulty fuel injector or damaged fuel pump assembly can cause fuel system to run lean Exhaust Leaks If there is an exhaust leak outside air can be pulled into the exhaust and past the 02 sensor causing a false lean 98 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 221 Closed Loop Multiplier High Gasoline Sep An OO Vale Ye _ Ne 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent section Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine to full operating temperature and then idle for a minimum of 2 minutes Does DST display HO2S voltage fixed below 0 35 volts after 2 minutes of idle run time Key OFF Disconnect HO2S sensor wire harness connector Disconnect ECM connector Using a high impedance DVOM Check for continuity between HO2S connector signal pin B and engine ground Do you have continuity Repair the Go to Step 4 circuit as required Refer to Wiring Repairs in Engine Electrical e Refer to Diagnostic aids for DTC 221 Did you check the diagnostic Aids for DTC 221 e Replace HO2S sensor Is the replacement complete Remove all test eguipment except the DST Connect an
192. heck Condition Engine Running Data Fault Condition ECT sensor voltage exceeds 4 95 Tem MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault deg P Closed Loop Enabled Circuit Description The ECT Engine Coolant Temperature sensor is a temperature sensitive resistor 201 4 located in the engine coolant It is used for the engine airflow calculation gasoline cold 181 9 enrichment and to enable other temperature dependant features The ECM provides a 163 1 voltage divider circuit so that when the coolant is cool the signal reads higher voltage and lower when warm This fault will set if the signal voltage is greater than 4 95 volts 2 anytime the engine is running The ECM will use a default value for the ECT sensor in the event of this fault HEN Mi 38 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 121 ECT VOLTAGE HIGH Csee Vw Ye No Did you perform the On Board OBD System Check Go to 2 Go to OBD System Check Section Go to step 3 Intermittent problem DST Diagnostic Scan Tool connected in System Go to Data Mode Intermittent Does DST display ECT voltage of 4 95 or greater section Key Off Bu Go to step 4 Go to Step 8 Disconnect the ECT sensor from the wiring harness and Jumper connector terminals A and B together Using a DVOM check the resistanc
193. ications 1 xl Ele Page Flash CommPort Plot Log Help mA Mania ina Linkerror attempting reconnect e Faults EE Controls Inc Connected 319200 s m Control and instrumentation Specialists Toggle Test Cell F10 FauftAccess _ MIL System 501095 DEW Varables Spe Cox Engine Speed 1027 rpm Running _ TPS command 38 z order dwell ms firing order voltage voltage Manifold Pressure 4 35 psia Fusi Type Gasoline TPS position a7 i pj 1 off na Coolant Temperature 97 6 Fuel Control Mode CL Active FPP command 00 2 2 as 2 orf 142 Cylinder Head Temp 976 degF Govemor switch state Gov FPP position 00 3 0 00 o2f 141 Manifold Temperature 78 9 degF Active governor type Mn TPS1 voltage 0596 volts osf Intake Air Temperature 787 degF Active govemor mode Droop TPS2 voltage 4267 volts 5 oof oo Vbat 138 volts Brake input level Open FPP1 voltage 0 434 volts 6 oof oo Vw 337 vots Oi cedido side OK FPP2 voltage 0 000 vols Hour meter 12828 hours IVS voltage 5 000 volts Cumulative starts 38 stats Glosed Loop PO eee EGOI 0882 vots Fuel select votage 104 vols Closed loop 1 00 z Fuel pump voltage 136 vots Injector kill Adaptive 1 00 1 voltage 206 vols DBW test mode EGO2 Eres Se 206 Wore Overspeedvollage 50 vols SnapShot SnapShot REJE uje Oil pressure voltage 58 vols uem Custom Adaplive 2 ma Defin
194. igure 4 2 2 Remove screw from solenoid connector switch and mounting 3 Rotate solenoid housing and remove sole noid and plunger spring 4 Remove end cap through bolts end cap washer and field frame figure 4 3 5 Remove center bearing plate screws and remove armature from housing figure 4 4 6 Slide thrust collar off armature shaft 7 Drive retainer ring collar toward armature THROUGH BOLT 22664 009 Figure 4 3 End Frame Removal IMPCO Technologies Engine Service Manual 3 1C5 Starter 4 BEARING PLATE ARMATURE 22664 010 Figure 4 4 Bearing Plate and Armature 8 Remove snap ring retaining collar clutch assembly and bearing plate CLEANING AND INSPECTION With the starter motor completely disassembled except for removal of field coils component parts should be cleaned and inspected Field coils should be removed only when defects are indicated by tests Defective parts should be replaced or repaired 1 Clean all starter motor parts Do not use dissolving agents for cleaning overrunning clutch armature and field coils Such a solvent would dissolve grease packed in clutch mechanism and damage armature and field coil insulation 2 Test overrunning clutch action Pinion should turn freely in overrunning direction and must not slip in cranking direction Check pinion teeth Check spring for tension and drive collar for wear Replace if necessary 3 Check that brush holders are
195. ine Diagnostic Trouble Codes 1C4 DTC 114 IAT Higher Than Expected 2 Motorola TMAP Diagnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged Inspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system If none of the above can be found Follow the diagnostic steps for 112 IAT Low Voltage IMPCO Technologies Engine Service Manual 33 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 115 01 Pressure Low ECM 5 volts Oil Pressure Voltage To Oil Pressure Switch Conditions for Setting the DTC 9 Engine Oil Pressure low Check Condition Engine running for 15 seconds and RPM greater than 1300 Fault Condition Open circuit voltage high MIL On during active fault and for 3 seconds after active fault Adaptive Enabled Closed Loop Enabled 9 Engine Shut Down Circuit Description The Oil Pressure Switch is used to communicate a low oil pressure condition to the ECM Engine damage can occur if the engine is operated with low oil pressure The ECM uses an analog voltage input with an internal 5 volt reference If the oil pressure circuit is grounded the input voltage will be near zero If it is open the input will be near 5 volts Th
196. ine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 142 check for any stored codes Does the engine operate normally with no stored codes 78 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 79 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 143 Never Crank Synced At Start ECM 5 volts Crank Sensor Conditions for Setting the DTC CKP Crankshaft Position Sensor Check Condition Engine cranking or running Adaptive Enabled Fault Condition 4 cranking revs without sync and engine RPM greater than 90 MIL On during active fault Closed Loop Enabled Circuit description The CKP Crankshaft Position Sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft It determines crankshaft position by monitoring the pulse wheel The Crankshaft position sensor is used to measure engine RPM and its signal is used to synchronize the ignition system The ECM must see a valid Crankshaft Position signal while cranking before it starts If no signal is present within 4 cranking revs this fault will set 80 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 143 Never Crank Sync At Start value ves No Did you pe
197. ing temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 111 check for any stored codes Does the engine operate normally with no stored codes 20 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 21 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 112 IAT Low Voltage Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Cranking or Running Fault Condition IAT Sensor Voltage less than 0 05 MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled and allowed to stay at limit if required but will then also set the limiting fault Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The is a calculated value based mainly on the sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow
198. ion x Check throttle shaft for sticking J J PX Check injector amp rails for leaks __ Engine Exhaust System P Inspect exhaust manifold forleaks T x Inspect exhaust piping for leaks SJ X Inspect catalyst inlet and outlet f x Check HEGO sensor connector _ The maintenance schedule represents manufacturers recommended maintenance intervals to maintain proper engine eguipment function Specific state and federal regulations may reguire eguipment operators to conduct comprehensive engine eguipment inspections at more periodic intervals than those specified above This maintenance schedule has no regulatory value and should not be considered representative of any state or federal engine eguipment maintenance reguirement IMPCO Technologies Engine Service Manual 9 OB Maintenance 4 3 liter Emission Certified GM Engine 10 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Fuel System Operation 1A1 SECTION 1A1 LPG FUEL SYSTEM OPERATION IMPCO Technologies Engine Service Manual 1 1A1 Fuel System Operation 4 3 liter Emission Certified GM Engine IMPCO SPECTRUM LPG FUEL SYSTEM WSs Tank Pressure Fuel Cylinder Regulated Pressure RA Intake Air Air Fuel Mixture Fuel Filter NIT Exhaust Gas
199. ipstick To ensure that you are not get ting a false reading make sure the following steps are taken before checking the oil level 1 Stop engine if in use 2 Allow sufficient time approximately 5 minutes for the oil to drain back into the oil pan 3 Remove the dipstick Wipe with a clean cloth or paper towel and reinstall Push the dipstick all the way into the dipstick tube 4 Remove the dipstick and note the oil level 5 Oil level must be between the FULL and ADD marks 4 3 liter Emission Certified GM Engine Maintenance OB DIPSTICK FULL MARK N ADD MARK Figure 2 Engine Oil Dip stick Typical 6 Ifthe oil level is below the ADD mark proceed to Step 7 and 8 and reinstall the dipstick into the dipstick tube 7 Remove the oil filler cap from the valve rocker arm cover 8 Add the required amount of oil to bring the level up to but not over the FULL mark on the dipstick 9 Reinstall the oil filler cap to the valve rocker arm cover and wipe any excess oil clean CHANGING THE ENGINE OIL IMPORTANT When changing the oil always change the oil filter 1 Start the engine and run until it reaches normal operating temperature IMPORTANT Change oil when engine is warm from operation as it flows more freely carrying away more impurities 2 Stop engine IMPORTANT Engine oil will be hot Use protective gloves to prevent burns Engine oil contains chemicals which may be harm
200. ir is cool the signal reads higher voltage and lower when warm The IAT is a calculated value based mainly on the IAT sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow This fault will set if the Intake Air Temperature is greater than 210 degrees F and engine RPM is greater than 1000 and Power Derate 1 will be enforced During this fault maximum throttle position is 50 and the MIL light will flash twice per second Diagnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged Inspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system 26 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 113 IAT Higher Than Expected 1 Bosch TMAP Diagnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged Inspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system e fnone of the above can be found Follow the diagnostic steps for DTC 112 Low Voltage Bosch T
201. ithin the test parameters of DTC 556 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 141 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 611 FPP High Voltage LT GRN RED 5 volts DK BLUE BLK LT GREEN Sensor Ground Conditions for Setting the DTC 142 Foot Pedal Position Check Condition Key On Fault Condition FPPI sensor voltage exceeds 4 8 MIL On during active fault and flashing at 2 Hz twice per second after active fault for the remainder of the key on cycle Adaptive Enabled Closed Loop Enabled Power Derate level 1 and Low Rev Limit enforced Circuit Description The Foot Pedal Position sensor uses a variable resistor to determine signal voltage based on pedal position Less depression of pedal results in lower voltage and greater depression results in higher voltage This fault will set if voltage is over 4 8 volts at any operating condition while the key is on If the voltage exceeds 4 8 then FPP is considered to be out of specifications At this point the ECM does not have a valid signal and must therefore enforce the low rev limit and Power Derate level 1 When these are enforced the maximum throttle position is 5096 and the maximum engine speed is 1600 RPM The Low Rev Limit is enforced for the remainder of the key on cycle Rev limit is still enforced if the a
202. itions Definitions Juntm_sec EMPTY Historic Faults Active Faults EMPTY EMPTY EMPTY Jar ______ EMPTY eem Emp CL BM2 EMPTY A EMI Flight Data FPP pot Custom TPS pct Definitions C EMPTY JEGOZ vas TRIM DC 7 The Spark Kill diagnostic mode allows the technician to disable the ignition on individual cylinders If the Spark Kill diagnostic mode is selected with the engine running below 1000 RPM the minimum throttle command will lock into the position it was in when the test mode was entered Ifthe Spark System Test mode is selected with the engine running above 1000 RPM the throttle will continue to operate normally Disabling Ignition Outputs To disable the ignition system for an individual cylinder use the mouse to highlight the Spark Kill button and select the desired The spark output can be re enabled by using the mouse to highlight the Spark Kill button and selecting Normal If the engine is running below 1000 RPM the spark output will stay disabled for 15 seconds and then re set Ifthe engine is running above 1000 RPM the spark output will stay disabled for 5 seconds and then re set This test mode has a timeout of 10 minutes Record the rpm drop related to each spark output disabled The Spark outputs are arranged in the order which the engine fires not by cylinder number 8 IMPCO Technologies Engine Service
203. ive battery cable Tighten AMMETER VOLTMETER R P M INDICATOR M CRANKING MOTOR Figure 4 15 No Load Test Typical Cable bolt to 15 N m 11 Ib ft NO LOAD TEST Figure 4 15 With the starter motor removed from the engine the pinion should be checked for freedom of rota 4 3 liter Emission Certified GM Engine tion by turning it on the shaft The armature should be checked for freedom of rotation by prying the pinion with a screwdriver If the armature does not turn freely The motor should be disassembled immediately However if the armature does rotate freely the motor should be given a no load test before disassembly Make connections as shown in figure 4 15 Close the switch and compare RPM current and voltage readings with the specifications If the specified current draw does not include the solenoid deduct from the armature reading the specified current draw of the solenoid hold in winding Make disconnections only with the switch open Use the test results as follows 1 Rated current draw and no load speed indi cates normal condition of the starter motor 2 Low free speed and high current draw indi cates Too much friction tight dirty or worn bear ings bent armature shaft allowing armature to drag Grounded armature This can be further checked on a growler after disassembly 3 Failure to operate with high current draw indicates A direct ground in the terminal
204. ive belt components Alcohol or Methanol base antifreeze or plain water are not recommended for use in the cooling system at anytime SERPENTINE BELT SYSTEM Serpentine belts utilize a spring loaded tensioner which keeps the belt properly adjusted Serpentine belts should be checked according to the maintenance schedule in this section IMPORTANT The engine manufacturer does not recommend the use of belt dressing or anti slipping agents on either belt con figuration COOLING SYSTEM It is important to remember that the cooling system of this engine be maintained properly to insure the longevity of the engine Maintenance of the cooling system is critical to not only the engine but the fuel system as well Because the LPG vaporizer is connected into the cooling system low coolant levels and restricted or plugged radiator cores can impact the performance of the fuel system Therefore proper mainte nance of the cooling system should include removing dust dirt and debris from the radiator core on regular intervals To properly maintain the cooling system follow the recommend maintenance schedule in this section Cooling system inspections should be performed as pre scribed when inspecting the cooling system check for the fol lowing e Plugged or restricted radiator core clean with com pressed air blow dust and debris from the core and the fan shroud e Check the radiator cap to insure proper sealing if damag
205. l hose to the FTV for kinks obstruction or leakage Replace the pressure trim valve PTV Refer to Pressure Trim Valve PTV Replacement ENT the fuel trim valve FTV Refer to Fuel Trim Valve FTV Replacement 1 Return the fuel system to normal operating condition 2 Observe the duty cycle reading 3 Raise the engine speed to approximately 2500 RPM 2096 8096 is the duty cycle in the specified range m Go to Step 25 Go to Step 22 NILI all vacuum hoses and mixer connec tions for leakage IMPCO Technologies Engine Service Manual 9 1B1 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine The fuel control system is operating normally Refer to Symptoms Diagnosis 1 Disconnect all test equipment 2 If you were sent to this routine by another dianostic chart retune to the previous diag nostic procedure System OK m mE LL au opo EEE 1 1 Disconnect all test equipment 2 Start the engine 3 Using a liquid leak detection solution leak check any fuel system repairs made System OK EE I HE O NE MEME EM 10 IMPCO Technologies Engine Service Manual SECTION 1B2 GASOLINE SYSTEM DIAGNOSIS IMPCO Technologies Engine Service Manual 1 1B2 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine GASOLINE FUEL SYSTEM DIAGNOSIS GASOLINE INJECTION SYSTEMS LJ FUEL PRESSURE GAUGE PRESSURE REGULATOR FUEL SUPPLY Figure 1 Gasoline Inje
206. l is communicated to the top of the air valve chamber through 4 vacuum ports in the air valve 4 3 liter Emission Certified GM Engine Fuel System Operation 1A1 assembly A pressure force imbalance begins to build across the air valve diaphragm between the air valve vacuum cham ber and the atmospheric pressure below the diaphragm The air valve vacuum spring is calibrated to generate from 101 6 mm 4 0 inches of water column at start to as high as 355 60 mm 14 0 inches of water column at full throttle The vacu um being created is referred to as Air Valve Vacuum AVV As the air valve vacuum reaches 101 6mm 4 0 inches of water column the air valve begins to lift against the air valve spring The amount of AV V generated is a direct result of the throttle position At low engine speed the air valve vacuum is low and the air valve position is low thus creating a small venturi for the fuel to flow As the engine speed increases the increases and the air valve is lifted higher thus creating a much larger venturi This air valve vacuum is communi cated from the mixer venturi to the LPR secondary chamber via the low pressure fuel supply hose As the AV V increases in the secondary chamber the secondary diaphragm is drawn further down forcing the secondary valve lever to open wider The mixer is eguipped with a low speed mixture adjustment which is retained in a tamper proof housing The mixer has been preset at the factory and shou
207. ld not reguire any adjust ment In the event that the idle adjustment should need to be adjusted refer to the Fuel System Repair section of this manual The air fuel mixer is an emission control device Components inside the mixer are specifically calibrated to meet the engines emissions reguire ments and should never be disas sembled or rebuilt If the mixer fails to operate replace with an OEM replace ment part Figure 6 Air Fuel Mixer Figure 7 Pressure Trim Valve and Fuel Trim Valve THROTTLE CONTROL DEVICE Drive By Cable Engine speed control is maintained by the amount of pressure applied to a foot pedal located in the operator s compartment A cable is utilized to connect the foot pedal to the throttle shaft in the engine compartment A coil spring mounted to the pedal and the throttle shaft will keep the throttle shaft in a normally closed position When the foot pedal is de pressed the throttle shaft is rotated opening the butterfly in the venturi of the throttle body allowing more air and fuel to enter the engine When the ECM detects that the engine has reached maximum governed speed or reguires adjustment for load the ECM will correct the throttle plate position by over IMPCO Technologies Engine Service Manual 5 1A1 Fuel System Operation 4 3 liter Emission Certified GM Engine riding the throttle shaft with the electronic governor The air fuel mixer is attached to the throttle control device or
208. le enrichment to enable certain features and for engine protection The ECM provides a voltage divider circuit so when the sensor reading is cool the signal reads higher voltage and lower when warm This fault will set if coolant temperature reaches 250 degrees F and engine RPM exceeds 650 rpm the engine will shut down IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 124 ECT Higher than expected 2 Value s Yes No Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 e Key On Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent e Warm Engine to normal operating temperature SECADA then run the engine above 1000 rpm for 60 seconds Does DST display ECT temperature of 235 degrees F or greater with the engine running over 650 rpm Verify with a temperature gauge that the engine Repair Cooling Go to step 4 coolant is over 225 degrees F system Does the temperature gauge indicate 230 degrees F or greater Verify ECT circuit function Follow diagnostic test procedure for DTC 122 ECT Low Voltage IMPCO Technologies Engine Service Manual 47 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 48 DTC 131 MAP High Pressure Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Manifold Absolute Press
209. le to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 514 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 127 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 515 Flash Checksum Invalid Microprocessor Conditions for Setting the DTC Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM has checks that must be satisfied each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 128 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 515 Flash Checksum Invalid
210. ll flash at 2 Hz for the remainder of the key on cycle This is a reminder that the Low Rev Limit is still enforced 146 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 612 FPP Voltage Low System Check cU ep DST Diagnostic Scan Tool connected in System Data made problem Go to ga a R ir the tep 5 Disconnect FPP sensor connector circuit as Inspect connector and wire terminals for damage Necessary corrosion or contamination Refer to Any problems found Wiring Repairs in Engine ey ON 5 0 Volts o to Step 6 epair the e Using A DVOM check for voltage at the FPP NM circuit as sensor connector between 5 volt reference pin A necessary and FPP sensor ground pin B Refer to Do you have voltage between them Wiring Repairs in Engine Electrical Disconnect FPP Sensor from wire harness Jumper 5 volt reference circuit pin A and FPP signal circuit pin C together e Key ON Does DST display FPP voltage of 4 8 volts or greater connector signal circuit p test light connected to battery voltage Does the DST display FPP voltage of 4 8 volts or circuit as necessary Refer to Wiring Repairs in Engine e Disconnect ECM wire harness connector e Using a DVOM check for continuity between FPP sensor connector 5 volt reference pin A and ECM connector 5 volt reference pin 50 Do you have continuity between them corrosion or contamination
211. llowing items Visually and physically inspect all electrical connections within the suspected circuit and or systems Check the scan tool data IMPCO Technologies Engine Service Manual 11 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Poor Fuel Economy DEFINITION Fuel economy as measured by refueling records is noticeably lower than expected Also the economy 15 noticeably lower than it was on this vehicle at one time as shown by an by refueling records Preliminary Checks Refer to Important Preliminary Checks Check the air cleaner element filter for dirt or being plugged Visually Physically check the vacuum hoses for splits kinks and proper connections Check the operators driving habits for the following items s there excessive idling or stop and go driving the tires at correct air pressure Are excessively heavy loads being carried 15 their often rapid acceleration Suggest to the owner to fill the fuel tank and to recheck the fuel economy Suggest that a different operator use the equipment and record the results Fuel System Checks e Check the LPR fuel pressure Refer to LPG Fuel System Diagnosis e Check the fuel system for leakage Sensor Checks e Check the Temperature Manifold Absolute Pressure TMAP sensor Ignition System Checks e Verify that the spark plugs are correct for use with LPG R42LTS e Checkthe spark plugs Remove t
212. lly due to a bent or unbalanced Remove the starter motor and check severe cases a knock as the starter armature the armature starter is coasting down to a stop after starting the engine 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Starter 1C5 SD300 STARTER MOTOR IDENTIFICATION Figure 4 1 The starter identification number is stamped into the starter motor end cap figure 4 1 Always refer to this number when servicing or ordering parts IDENTIFICATION NUMBER LOCATED ON BACK PLATE 22664 007 Figure 4 1 Starter Motor I D Number STARTER MOTOR MAINTENANCE The starter motor and solenoid are completely enclosed in the drive housing to prevent entrance of moisture and dirt Periodic inspection however is required as follows 1 Inspect terminals for corrosion and loose connections 2 Inspect wiring for frayed and worn insula tion 3 Check the mounting bolts for tightness STARTER MOTOR REMOVAL WARNING Disconnect battery cables at battery before removing starter 1 Disconnect battery cables from battery 2 Disconnect wires from starter solenoid terminals 3 Remove starter mounting nuts 4 Pull starter assembly away from flywheel and remove it from engine STARTER MOTOR DISASSEMBLY Figure 4 2 through 4 4 CONNECTOR MOUNTING SCREW 2 22664 008 Figure 4 2 Solenoid Screw Removed 1 Remove solenoid screws f
213. low sensor can cause a rich condition and set this DTC Refer to DTC P0101 Using scan tool review Failure Records If intermittent condition is suspected refer to Intermittent Conditions Test Description The numbers below refer to the step numbers on the diagnostic table 5 If conditions were not corrected refer to Fuel System Diagnostic for possible fuel problem 6 An EVAP canister that is saturated will cause a rich condition Fuel in the vacuum line to the fuel pressure regulator indicates leaking regulator If conditions were not corrected a worn cam worn intake or exhaust valves or other engine mechanical failure may be at fault DTC P0172 or P0175 Did you perform the Diagnostic System Check Engine 1 Controls Important If any DTCs are set other than P0172 refer to Does the scan tool indicate that the Long Term Fuel Trim those DTCs before continuing 1 Install scan tool 2 Start and idle the engine at the normal operating temperature in closed loop 2 Record the Long Term Fuel Trim data Turn OFF the engine Turn ON ignition with the engine OFF Review the Freeze Frame Records and or Failure Records and record displayed data for this DTC is less than the specified value Go to Diagnostic System Check Engine Controls 13 Go to Step 3 IMPCO Technologies Engine Service Manual 11 Go to Diagnostic Aids 1C7 Ignition System 4 3 liter Emission Certified GM Engine DTC
214. ls recommended by the engine manufacturer already contains a balanced additive treatment The uses of supplemental additives which are added to the engine oil by the customer are not necessary and may be harmful The engine manufacturer fuels system suppliers and engine dis tributors do not review approve or recommend such products SYNTHETIC OILS Synthetic oils have been available for use in industrial en gines for a relatively long period of time Synthetic oils may offer advantages in cold temperature pumpability and high temperature oxidations resistance However synthetic oils have not proven to provide operational or economic benefits over conventional petroleum based oils in industrial engines Their use does not permit the extension of oil change inter vals 4 IMPCO Technologies Engine Service Manual CHECKING FILLING ENGINE OIL LEVEL Overfilled crankcase oil level being to high can cause an oil leak a flucua tion or drop in the oil pressure and rocker arm clatter on engines The overfill condition results in the engine crankshaft splashing and agitating the oil causing it to foam become aereated The aereated oil causes the hydraulic lifters to bleed down This results in rocker arm clatter and loss of engine performance due to valves not opening properly IMPORTANT Care must be taken when checking engine oil level Oil level must be maintained between the ADD mark and the FULL mark on the d
215. lt reference pin 3 and engine ground Do you have continuity and terminals for corrosion contamination or mechanical damage Any problems found Replace M Refer to M replacement in the Engine Controls Section Check for continuity between TMAP sensor connector signal circuit pin 4 and ECM signal PIN 33 Do you have continuity between them y connector signal pin 4 and engine ground Do you have continuity connector terminals for corrosion contamination or mechanical damage Any problems found M replacement in the Engine Controls Section Is the replacement complete Replace TMAP sensor Is the replacement complete 58 IMPCO Technologies Engine Service Manual u o to step 10 Repair the circuit as necessary Refer to Wiring Repairs in Engine Repair the o to tep circuit as necessary Refer to Wiring Repairs in Engine Repair the o to Step 16 circuit as necessary Refer to Wiring Repairs in Engine T o lo Step 14 epair the circuit as necessary Refer to Wiring Repairs in Engine Electrical epair the o to step 15 circuit as necessary Refer to Wiring Repairs in Engine Electrical epair the o to Step 16 circuit as necessary Refer to Wiring Repairs in Engine Electrical de o to step 1 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 ystem OK Connect any disconnected components fuses etc System Check Using the DST clear DTC
216. ltage applied to the pump pressure should rise above 325 kPa 47 psi as the valve in the return pipe is par tially closed NOTICE Do not allow the pressure to exceed 414 kPa 60 psi as damage to the regulator may result 17 Fuel pressure above 325 kPa 47 psi may cause a rich 4 3 liter Emission Certified GM Engine LPG Fuel System Diagnostics 1B2 starting followed by black smoke and a strong sulphur smell in the exhaust 18 This test is to determine if the high fuel pressure is due to a restricted fuel return pipe or a faulty fuel pressure regulator 21 The pressure regulator may be fitted with a screen which is designed to trap contaminants introduced dur ing engine assembly If dirty it can be removed with a small pick and discarded without potential harm to the regulator 23 system that does not hold pressure is caused by one of the following e Leaking fuel pump check ball e Leaking fuel feed hose e Leaking valve seat within the pressure regulator e Leaking injector 26 A leaking injector can best be determined by check ing for a fouled or saturated spark plug s If a leaking injector can not be determined by a fouled or saturated plug the following procedure should be used e Remove the fuel rail but leave the lines con nected e Lift the fuel rail out just enough to leave in jector nozzle s in the ports To reduce the risk of fire or personal injury that may result form fuel spray o
217. lves which are normally set at 25 8 bar 375 psi to prevent tank rupture due to over pressurization of the cylinder The service valve mounted in the end of the cylinder controls the flow of fuel from the tank By turning the handle to its open position fuel flows out of the tank and into the service line The service valve is also equipped with a safety feature called an excess flow check valve This feature reduces the flow from the service valve in the event of a rupture of the fuel line or any down stream disconnect coupling when applicable component Figure 2 Typical Propane Cylinders SERVICE LINE Propane flows from the fuel tank to the electric lock via the service line The service line is connected to the tank utiliz ing a quick coupler The other end of the service line is con nected to a bulkhead connector mounted on the equipment sheet metal This bulkhead connector allows for a safe means of passing through the equipments engine compartment sheet metal and into the engine compartment Ifa bulkhead con nector is used a pressure relief device is mounted in the ser vice line or the connector itself to prevent over pressurization ofthe service line The service line is made of high pressure hose with special material or possibly tubing which is com patible with the LPG fuel and should always be replaced with an OEM supplied part The bulkhead assembly should never be removed and a service lin
218. may be ightly dlubrieated with Bearing in drive end housing is a roller SR ADD LUBRICANT If replace the drive end housing bearing using a small bearing puller recessed 0 25 mm 0 01 in into casting figure 4 21 Replace bearings when damaged 12 VOLT BATTERY FIELD LEAD DISCONNECTED MOMENTARY GROUND ELECTRICAL CONNECTIONS Figure 4 22 Checking Pinion Clearance Starter 1C5 6 Drive and shaft assembly into drive end housing Use a screwdriver to gently guide shift lever over shift collar pins on drive assem bly CAUTION Field frame magnets have strong attraction to armature Keep fingers clear of pinch points to avoid personal injury 7 Shield field frame and armature to drive end housing Inspect Brushes When damaged excessively worn replace brush holder assembly 8 Brush holder assembly onto armature 9 Commutator end frame to brush assembly using screws Tighten Screws to 6 5 Nem 60 Ib in 10 Through bolts PRESS ON CLUTCH TO REMOVE SLACK PINION STOP COLLAR 0 25 mm TO 4 06 mm 0 010 in TO 0 160 in PINION CLEARANCE FEELER GAGE CHECKING CLEARANCE 131 163 131 163 IMPCO Technologies Engine Service Manual 7 1C5 Starter 4 3 liter Emission Certified GM Engine 8 Tighten Through bolts to 8 5 75 Ib in Measure Al Pinion clearance refer to Checking Pinion Clearance in
219. me voltage Then the PCM assigns a voltage value The and updates the Failure Records PCM checks the knock sensor and related wiring SIO ID 727824 by comparing the actual knock signal to the assigned u voltage range A normal KS signal should stay Conditions for Clearing the MIL DTC within the assigned voltage range This DTC will set if The control module turns OFF the malfunction the PCM malfunctions in a manner that will not indicator lamp MIL after 3 consecutive ignition allow proper diagnosis of the KS system cycles that the diagnostic runs and does not fail Conditions for Running the DTC A current DTC Last Test Failed clears when the diagnostic runs and passes The engine run time is more than 10 seconds A history DTC clears after 40 consecutive warm up Conditions for Setting the DTC cycles if no failures are reported by this or any The PCM detects a malfunction in the KS diagnostic other emission related diagnostic circuitry that will not allow proper diagnosis of the Clear the MIL and the DTC with a scan tool KS system SIO ID 727820 Diagnostic Aids Action Taken When the DTC Sets The knock sensor must be torqued correctly to The control module illuminates the malfunction NM de bt indicator MIL on the second consecutive The mounting between the sensor and engine ignition cycle that the diagnostic runs and fails must be free of burrs casting flash and foreign The control module recor
220. n Cranking or Running Fault Condition Throttle command is 20 less than throttle position for 200ms or longer MIL On during active fault Adaptive Enabled Closed Loop Enabled Engine Shut Down Circuit Description 160 There are 2 Throttle Position Sensors located within the throttle which use variable resistors to determine signal voltage based on throttle plate position TPS1 will read low voltage when closed and TPS2 will read high voltage when closed The TPS1 and TPS2 percentages are calculated from these voltages Although the voltages are different the calculated values for the throttle position percentages should be very close to the same The TPS values are used by the ECM to determine if the throttle is opening as commanded This fault will set if the throttle command is 20 less than the actual throttle position During this active fault the MIL light will be on and the engine will shut down IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 638 Throttle Unable to Close Value s m Did you perform the On Board OBD System Check Key ON Engine OFF DST Diagnostic Scan Tool connected in DBW Drive By Wire test mode Depress Foot Pedal until theThrottle Command is between 63 68 Is the TPS 1 voltage greater than 2 0 volts e Key OFF e Disconnect wire harness connector from throttle e Probe TPS 1 signal circuit with t
221. n Taken When the DTC Sets The control module illuminates the malfunction indicator lamp MIL on the second consecutive ignition cycle that the diagnostic runs and fails The control module records the operating conditions at the time the diagnostic fails The first time the diagnostic fails the control module stores this information in the Failure Records If the diagnostic reports a failure on the second consecutive ignition cycle the control module records the operating conditions at the time of the failure The control module writes the operating conditions to the Freeze Frame and updates the Failure Records SIO ID 727824 Conditions for Clearing the MIL DTC The control module turns OFF the malfunction indicator lamp MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail A current DTC Last Test Failed clears when the diagnostic runs and passes A history DTC clears after 40 consecutive warm up cycles if no failures are reported by this or any other emission related diagnostic Clear the MIL and the DTC with a scan tool Diagnostic Aids The KS must be correctly tightened to 25 N m 18 Ib ft The mounting between the sensor and engine must be free of burrs casting flash and foreign material The KS head is clear from hoses brackets and engine wiring f an intermittent is suspected refer to Intermittent Conditions Test Description The n
222. n sensor HO2S voltage signals Long Term fuel trim makes coarse adjustments in order to maintain Air Fuel Ratio of 14 7 1 The fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission EVAP canister is causing a rich condition If the PCM detects an excessively rich condition this DTC will set If the PCM detects excessive vapor then a pass is logged Conditions for Running the DTC DTCs P0101 P0103 P0108 P0135 P0137 P0141 P0200 P0300 P0410 P0420 P0430 P0440 P0442 P0443 P0446 P0449 P0506 P0507 or P1441 are not set The engine coolant temperature ECT is between 75 115 C 167 239 F The intake air temperature 1 is between 20 to 90 C 4 194 The manifold absolute pressure MAP is between 26 90 kPa 3 7 13 psi The vehicle speed is less than 137 km h 85 mph The engine speed is between 400 3 000 RPM The barometric pressure BARO is more than 74 kPa 10 7 psi e The mass airflow MAF is between 5 90 g s The fuel level is more than 10 percent The throttle position is less than 90 percent Conditions for Setting the DTC The average long term fuel trim value is below 13 percent All of the above conditions are present for 40 seconds Diagnostic Aids Fuel contamination such as water and alcohol will effect fuel trim A malfunctioning Mass Air F
223. n sensor is used to synchronize the fuel and ignition systems This fault will set if the ECM detects erroneous pulses from the camshaft position sensor causing invalid cam re sync The engine will not run with this fault present 88 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 145 Camshaft Sensor Noise vs m Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to Step 3 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical e Key On Engine OFF 5 0 volts Go to Step 4 Repair the circuit e Disconnect the CMP Camshaft position Sensor as necessary connector C011 Refer to Wiring e Using A DVOM check for voltage at the CMP Repairs in Engine sensor connector pin C and engine ground Electrical Do you have voltage Key OFF Go to Step 5 Repair the circuit Disconnect ECM connector C001 as necessary Using a DVOM check for continuity between CMP Refer to Wiring Repairs in Engine Electrical Go to Step 6 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to Step 7 as necessary Refer to Wiring Repairs in Engine Electrical connector pin A and ECM connector pin 14 Do you have continuity between them Repair the circuit Go to step 8 as necessary Refer to Wiring Repairs in Engine Electrical m mE Go to
224. n the engine make sure fuel rails is positioned over injector port and injec tor retaining clips are intact e Pressurize the fuel system and observe injector nozzles Gasoline Fuel System Diagnosis Value Were you referred to this procedure by a DTC diag nostic chart p Go to Step 3 Go to Step 2 Perform the On Board Diagnostic OBD System Check Go to the ap plicable DTC Are any DTCs present in the ECM Table Verify that the Gasoline fuel tank has a minimum of Go to Step 4 Go to Step 3 1 4 tank of fuel Does the vehicle have fuel Connecta fuel pressure gage at the Schrader Valve located on the fuel rail Ignition ON fuel pump will run Note the pressure 285 325 kPa Turn ignition off pressure may vary slightly then 41 47 psi hold steady Go to Step 5 Go to Step 10 Is pressure within specified values Did the fuel pressure hold study after the pump stopped m Go to Step 6 Go to Step 22 IMPCO Technologies Engine Service Manual 3 1B2 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine 1 Start engine allow it to warm to normal operat ing temperature at idle 2 Fuel pressure noted in step 4 should drop 21 69 kPa 3 Did pressure drop by the specified value 10 psi Go to 27 Go to Step 7 Disconnect the vacuum hose from the pressure regulator With the engine idling apply 12 14 inches of vacuum to the pressure regulator pressure 21 69 kPa 3 should drop Did th
225. nal 5V Reference Higher Than Expected Key ON Engine running DST Diagnostic Scan Tool connected in System Data Mode Does DST display DTC 532 Check all ECM ground connections Refer to Engine electrical power and ground distribution Are the ground connections Ok Key OFF Disconnect ECM connector Key ON Using DVOM check for Voltage between ECM harness wire LT GRN R pin 50 and engine ground Do you have voltage Remove all test eguipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 532 check for any stored codes Does the vehicle engine normally with no stored codes IMPCO Technologies Engine Service Manual Ye No Go to Step 2 Go to OBD System Check Section Go to Step 3 Intermittent problem Go to Intermittent section Go to Step 4 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to Step 5 as necessary Refer to Wiring Repairs in Engine Electrical System OK Go to OBD System Check 137 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 555 RTI 2 Loss Microprocessor Conditions for Setting the DTC
226. nce OB _ po Date Daily 250 500 750 1000 1250 1500 1750 2000 General Maintenance Section TE PR RR ee oa Check engine cil leve __ 4 P Check coolantlevek _____ X Every 100 hours or 60 days of operation Prior to any service or maintenance activity Inspect Accessory Drive belts X Inspect electrical system x Inspect all vacuum lines and fiting J X Inspect all fuel lines and fitting T x Engine Coolant Section J T Checkcoolantlevel Ax 4 l1 evo 100 LIT or 60 EE of rp Change coolant ________ coolant Inspect coolant hoses for cracks ee xl I L e Engine Ignition System Inspect Battery case for damage J x Inspect battery cables do o x x Check all electricalconnectors X Check ignition timing andadjut x Replace sparkplugs o o doo PX ___ _______ Replace fuel fiter x x ____ PP x Ensuelockoffcosing oo oo So x Test LPG Gas regulator pressure J X Check air induction system for leaks J x Check manifold for vacuum leaks Check FTV electrical connect
227. ndicate the throttle blade angle for speed control and load control as well as emission control At the opposite end of the throttle shaft cable end is the Foot Pedal Position FPP sensor which indicates the posi tion of the throttle pedal Also mounted to the throttle control device is an integrated electronic governor The throttle control is maintained by a foot pedal located in the operator s compartment and con nected to the throttle control device by a cable The governor is controlled by the ECM and has no external adjustments When the ECM determines load adjustment or maximum engine speed has been achieved the governor overrides the throttle shaft and corrects the throttle blade position Foot Pedal Position Sensor Throttle Position Sensor EUM Motor Figure 3 Throttle Control Device Drive By Cable Throttle Body Assembly THREE WAY CATALYTIC MUFFLER The emission certified engine has been designed and calibrat ed to meet the emission standards in effect for 2004 To help meet the emission requirements the vehicle has been equipped with a three way catalytic muffler The catalyst muffler is a three way catalyst sound damping and spark arresting unit Besides controlling the noise created from the combus tion process and preventing sparks from escaping from the exhaust system the most important function is treating the exhaust gases which are created from the combustion process The three way catalyst consists of
228. ne Cover Replacement in Interior Trim Disconnect the fuel injector harness connector Refer to Engine Wiring LH Side Electrical in Wiring Systems Turn ON the ignition with the engine OFF Probe the ignition 1 voltage supply circuit of the appropriate fuel injector with a test lamp that is connected to a good ground Does the test lamp illuminate Go to Step 5 Go to Step 11 1 Connect the J 34730 375 Fuel Injector Test Lamp between the control circuit and the ignition 1 voltage supply circuit of the appropriate fuel injector 2 Crank the engine Does the test lamp flash Go to Step 9 Go to Step 6 Does the test lamp remain illuminated at all times Go to Step 8 Go to Step 7 Test the control circuit of the fuel injector for an open and for a short to voltage Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 10 Test the control circuit of the fuel injector for a short to ground Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 13 Inspect for poor connections at the harness connector of the fuel injector Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 12 Inspect for poor connections at the harness connector of the PCM Refer to Testing for Intermitt
229. ne if the throttle is opening as commanded This fault will set if voltage is above 4 8 volts at any operating condition while the engine is cranking or running The engine will not start or run during this active fault 150 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 631 TPS 1 Signal Voltage High System Check ection voltage problem Does TPS 1 voltage ever exceed 4 8 volts Go to Jo Repair the Disconnect ECM wire harness connector circuit as Key ON necessary Using aDVOM check for voltage between TPS 1 Pero signal at the ECM connector pin 53 and engine Mining Repairs in Engine Electrical side of the wire harness pin 49 with a test light connected to battery voltage Does the test light come on electrical connector terminals for damage corrosion or contamination circuit as Did you find a problem necessary Refer to Wiring Repairs in on Repair the Disconnect ECM connector circuit as Using a DVOM check for continuity between the necessary TPS 1 connector sensor ground pin and ECM Referto connector TPS 1 sensor ground pin 49 Wiring Repairs Do have continuity between them in Engine IMPCO Technologies Engine Service Manual 151 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine emove all test equipment except DSI ystem OK Connect any disconnected components fuses System Check etc Using the DST clear D
230. ng a soapy solution or an electronic leak detector if leaks are detected make repairs LOW PRESSURE REGULATOR MAINTENANCE AND INSPECTION IMPORTANT The Low Pressure Regulator LPR components have been specifically designed and calibrated to meet the fuel system requirements of the emission certified engine The regulator should not be disassembled or rebuilt If the LPR fails to op erate or develops a leak the LPR should be replaced with the OEM recommended replacement parts When inspecting the regulator check for the following items Check for any fuel leaks at the inlet and outlet fittings Check for any fuel leaks in the regulator body Check the inlet and outlet fittings of the coolant supply lines for water leaks Check the coolant supply lines for hardening cracking chaffing or splits If any of these conditions exist replace coolant lines Check coolant supply hose clamp connections ensure they are tight Check the to ensure the Pressure Trim Valve PTV mounting bolts are secure Check PTV for external damage Check PTV electrical connection to ensure the connector is seated and locked Check to ensure the regulator is securely mounted 4 3 liter Emission Certified GM Engine Maintenance OB CHECKING DRAINING OIL BUILD UP IN THE LOW PRESSURE REGULATOR During the course of normal operation oil or heavy ends may build inside the secondary chamber of the Low Pressure Regulator LPR These oil and
231. nk 1 sensor 1 HO2S bank 2 sensor 1 and HO2S bank 1 sensor 2 A condition in any sensor will cause this DTC to set Measure the resistance between the HO2S ignition 1 voltage circuit sensor side and the HO2S heater ground circuit sensor side Refer to Circuit Testing in Wiring Systems Does the resistance of any sensor measure above or below the specified range Inspect for poor connections at the harness connector of the affected HO2S Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems Did you find and correct the condition Inspect for poor connections at the harness connector of the PCM Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems Did you find and correct the condition Repair the open in the ignition 1 voltage circuit Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you complete the repair Repair the open in the HO2S heater ground circuit Refer to Wiring Repairs in Wiring Systems Did you complete the repair Replace the affected HO2S refer to Heated Oxygen Sensor HO2S Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor HO2S Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor HO2S Replacement Bank 2 Sensor 1 Did you complete the replacement 6 IMPCO Technologies Engine Service Manual Values Go to Step 13 Go to Step 12 Go to Step 16 Go to Step 20 Go to Step 20 Go to Step 18 Go t
232. nning The ECM will use the default value for the sensor in the event of this fault 14 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 111 IAT VOLTAGE HIGH BOSCH TMAP Action Value sh Yes No Did you perform the On Board OBD System Check o to Step o to OBD System Check Section o to step problem DST Diagnostic Scan Tool connected in Go to Intermittent T disr section o to step 9 o to step 4 Disconnect the TMAP sensor connector from the wiring and harness and jumper pins 1 and 2 together Key On Does the DST display IAT voltage of 0 1 volts or less Jumper TMAP sensor connector signal pin 2 to engine ground Key ON Does DST display IAT voltage of 0 1 volts or s Disconnect the ECM wire harness connector circuit as Check for continuity between TMAP sensor necessary connector signal pin 2 and ECM IAT signal pin 32 Refer to Do you have continuity between them Wining Repairs in Engine epalr the connector ground circuit pin 1 and ECM sensor Go to step 10 circuit as ground circuit pin 49 necessary Do you have continuity between them Refer to Wiring Repairs 2 cae Repair connectors for damage corrosion or circuit as contamination necessary Were any problems found Refer to Wiring Repairs in Engine Electrical Repair the connectors for damage corrosion or circuit as contamination necessary Were any
233. nostic table 5 This step will determine if the and and fuel supply system are functioning properly The vacuum on the secondary test port will be approximately 1 0 to 2 0 w c 6 This step checks the base mechanical LPR output pres sure by disabling all fuel control devices 9 This step checks for proper air valve operation 19 This determines if fuel is available from the fuel tank supply system 4 3 liter Emission Certified GM Engine LPG Fuel System Diagnostics 1B1 LPG Fuel System Diagnosis 1 Were you referred to this procedure by a DTC diag Go to Step 3 Go to Step 2 2 Perform the On Board Diagnostic OBD System Check Go to the ap plicable DTC Table Go to Step 3 3 Verify that the LPG fuel tank has a minimum of 1 4 tank of fuel that the manual valve is open and the tank guick connect is fully engaged Go to Step 4 Does the vehicle have fuel 4 Connect a water column gauge or 2 Does the engine start and run Go to Step 5 Go to Step 8 5 With the engine idling observe the pressure read ing for the LPR secondary pressure Does the fuel pressure fluctuate rhythmically OUTSIDE the specified range Go to Step 25 Go to Step 6 Are any DTCs present in the ECM eter to the secondary test port of the low pres sure regulator LPR Start the engine and allow it to reach operating temperature 1 Disconnect the PTV 8 FTV electrical connec tors Note This action may ca
234. ns Check the operators driving habits for the following items s there excessive idling or stop and go driving the tires at the correct air pressure Are excessively heavy loads being carried 15 their often rapid acceleration Suggest to the owner to fill the fuel tank and to recheck the fuel economy Suggest that a different operator use the equipment and record the results Fuel System Checks e Check the fuel Rail pressure Refer to Gasoline Fuel System Diagnosis e Check the fuel system for leakage Sensor Checks e Check the Temperature Manifold Absolute Pressure TMAP sensor Ignition System Checks e Verify that the spark plugs are correct use R42LTS e Checkthe spark plugs Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits e Check the ignition wires for the following items Cracking Hardness Proper connections Cooling System Checks e Checkthe engine thermostat for always being open or for the wrong heat range Additional Check e Check the transmission shift pattern Refer to the OEM Transmission Controls section the Service Manual e Check for dragging brakes 26 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Rough Unstable or Incorrect Idle Stalling DEFINITION The engine runs unevenly at idle I
235. nsors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The IAT is a calculated value based mainly on the IAT sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow This fault will set ifthe signal voltage is more than 4 95 volts anytime the engine is running The ECM will use the default value for the sensor in the event of this fault 18 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 111 IAT VOLTAGE HIGH MOTOROLA u Value s Yes No Did you perform the OBD System Check Go to m 2 Go to OBD System Check Section Go to step 3 Intermittent problem Go to Intermittent section Go to step 9 Go to step 4 IN Go to Step 7 Go to Step 6 5 Replace TMAP sensor Go to Step 11 Is the replacement complete e KeyOn DST Diagnostic Scan Tool connected in System Data Mode Does DST display IAT voltage of 4 95 or greater Key Off Disconnect the TMAP sensor connector from the wiring and harness and jumper pins A and B together Key On Does the DST display IAT voltage of 0 1 volts or less Key OFF Jumper TMAP sensor connector signal pin B to engine ground Key ON Does DST display IAT voltage of 0 1 volts or less e Check for continuity between TMAP
236. nstallation Procedure IMPORTANT e Apply a small amount of lubricant to the TMAP o ring 4 Install TMAP 5 Secure using the two 2 retaining bolt Tighten 6 Nm 54 in Ibs 6 Connectthe TMAP electrical connector Start engine 8 Install diagnostic service tool and check for DTC codes and MIL lights ENGINE CONTROL MODULE REPLACEMENT Disconnect Negative battery cable Remove controller from mounting bracket Push connector lock back to unlock connector Unplug controller and remove Installation Procedure IMPORTANT Controller is calibrated for each engine verify you have the correct controller Plug connector into controller Push lock into place Mount controller into mounting bracket Reconnect the battery cable Jo po cd Qv m Install Diagnostic service tool IMPCO Technologies Engine Service Manual 11 1E1 Fuel System 10 Start engine 11 Check for any DTC codes and clear 12 Verify engine is in closed loop and no MIL lights are present HEATED EXHAUST GAS OXYGEN SENSOR REPLACEMENT 1 Disconnect Negative battery cable 2 Disconnect the O 2 sensor electrical connector 3 Using a O 2 Sensor socket remove the O 2 Sensor and discard Installation Procedure IMPORTANT e Before install the O 2 sensor lubricate threads with anti seize compound GM P N 5613695 or equiva lent Avoid getting compound on the sensor tip 4 Install O 2 sensor Tighten 41 Nem 30 lb ft 5 Start engine
237. nual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 652 Fuel Rev Limit Value s Yes mo 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section e Key ON Engine OFF Go to Step 3 Go to Step 4 e DSTin Active Fault Mode mE Are any other DTC codes present with DTC 651 Go to Step 6 Go to Step 5 Go to Step 8 Go to Step 7 e Diagnose any other DTC codes before proceeding with this chart Have any other DTC codes been diagnosed and repaired e Check the Service Part Number on the ECM to ensure correct calibration is in use Is the Service Part Number Correct e Replace ECM with correct Service Part Number Is the replacement complete e Check the mechanical operation of the throttle 2 3 4 5 Is the mechanical operation of the throttle OK e Check engine for large manifold vacuum leaks Refer to Fuel Systems Section 1B Symptom Diagnostics Go to Step 9 Go to OBD System Check Section System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 167 Did you find and correct the vacuum leak Remove all test equipment except the DST Connect any disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and drivea
238. o Step 19 Go to Step 15 Go to Testing for Intermittent and Poor Connections Go to Step 20 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0140 cont d Sep Replace the PCM Refer to Powertrain Control Module PCM Replacement Did you complete the replacement Go to Step 22 With a scan tool observe the stored information Capture Info Does the scan tool display any DTCs that you have not diagnosed O Use the scan tool in order to clear the DTCs 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text Does the DTC run and pass Go to Step 23 Go to Step2 Go to Diagnostic Trouble Code DTC List System OK IMPCO Technologies Engine Service Manual 7 1C7 Ignition System 4 3 liter Emission Certified GM Engine 8 vin my Bee Circuit Description The powertrain control module PCM controls the air fuel metering system in order to provide the best possible combination of driveability fuel economy and emission control Fuel delivery is controlled differently during open and closed loop During Open Loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input During Closed Loop the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments If the
239. o ensure that cross firing is not occurring If the misfire occurs when the weather is damp the problem could be due to worn plug wires Inspect the fuel for the following conditions Condition and quality Dirty or contaminated fuel could cause a misfire condition The fuel level lf the fuel level is low the fuel pump may draw air into the fuel rail causing a stumble and a possible misfire condition Inspect the fuel trim number in the Freeze Frame in order to determine if this has occurred This condition would be likely if the short term fuel number was more than 20 Restrictions A restricted fuel filter can also cause a misfire Inspect for sticking intake or exhaust valves on engines which misfire when the engine is cold Inspect the heated oxygen sensor HO2S for abnormal voltage readings Inspect for a vacuum leak as a possible cause of the engine misfire An intermittent may be caused by any of the following conditions poor connection Rubbed through wire insulation A broken wire inside the insulation Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint Refer to Testing for Intermittent and Poor Connections in Wiring Systems If a repair is necessary refer to Wiring Repairs in Wiring Systems Test Description The numbers below refer to the step numbers on the diagnostic table 2002 Van August 7 2001 IMPCO Technologies Engine Ser
240. o obvious reasons for the excessive back pressure the catalytic converter is suspected to be restricted and should be replaced using current recommended procedures 1 BACK PRESSURE GAGE 3 2 OXYGEN SENSOR 02S EXHAUST MANIFOLD Figure 1 Exhaust Back Pressure Test IMPCO Technologies Engine Service Manual 29 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine 30 IMPCO Technologies Engine Service Manual SECTION 1 2 WIRING SCHEMATICS IMPCO Technologies Engine Service Manual 1 1C2 Wiring Sci ti 1 3 liter Emission Certified GM Engi ON VEHICLE SERVICE WIRE HARNESS REPAIR The ECM PCM harness electrically connects the ECM PCM to the various solenoids electrically and sensors in vehicle engine and passenger compartment Wire harnesses should be replaced with proper part number harnesses When signal wires are spliced into a harness use wire with high temperature insulation only With the low current and voltage levels found in the system it is important that the best possible bond at all wire splices be made by soldering the splices as shown in Figure 3 20 Molded on connectors require complete replacement of the connector This means splicing a new connector assembly into the harness Refer to Figure 1 for wiring diagrams CONNECTORS AND TERMINALS Use care when probing a connector or replacing terminals in them It is possible to short between opposite terminals If this happens to the wrong termin
241. o the fuel delivery based on feedback from the HEGO The closed loop multiplier is expressed as a percentage and is not stored in the ECM s memory Fuel and timing modified based on feedback from the O2 sensor Drive by wire Diagnostic Trouble Code A code which is stored in the ECM when an ECM initiated test fails Engine Coolant Temperature Engine Control Module The computer which controls the fuel and ignition system on the engine See HO2S Foot Pedal Position Heated Oxygen Sensor Intake Air Temperature Idle Validation Switch Manifold Absolute Pressure The pressure of the air in the intake manifold Manifold Air Temperature The temperature of the air in the intake manifold Malfunction Indicator Light A dash mounted light that illuminates when the ECM senses a system fault Milli seconds 1 1000 of a second Fuel and timing based strictly on tables stored in the ECM Pounds per square inch absolute 14 7 psia 0 psig Random Access Memory The portion of computer memory within the ECM which changes as the en gine is running and is stored while the engine is off Throttle Position Sensor The throttle position sensor measures the opening of the throttle 2 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DIAGNOSTICS OVERVIEW OF THE SPECTRUM FUEL SYSTEM The Spectrum Fuel system has built in diagnostics for trouble shooting The system has a dash mo
242. o the mounting bracket using the two 2 retaining bolts and tighten to specification Tighten 14 Nm 10 ft Ibs Install the water inlet and outlet lines to the fittings and place clamps Install the water inlet and outlet lines to the fittings and place clamps Install LPL Refer to Low Pressure Lock off Replacement Install the PTV Refer to Pressure Trim Valve Replacement Tighten fuel line fitting Tighten 27 Nm 20 ft Ibs Replace the drained coolant Start the vehicle and leak check the propane fuel system at each serviced fitting Figure 3 4 3 liter Emission Certified GM Engine Fuel System 1E1 FUEL TRIM VALVE FTV SOLENOID 6 Install the two bolts REPLACEMENT 7 Tighten retaining bolts Figure 3 Tighten 9 Nem 80 Ib in 8 Connect Fuel supply hose Disconnect the FTV electrical connection 9 Connect electrical connection Removal Procedure Remove the fuel supply hose from the FTV 10 Start the vehicle Remove the two 2 retaining bolts and retain Remove the FTV Rov TEMPERATURE MANIFOLD ABSOLUTE PRESSURE TMAP Installation Procedure Figure 3 IMPORTANT Removal Procedure Apply a small amount of O ring lubricant to the 1 Disconnect the TMAP electrical connector PTV o ring before installation 2 Remove the two retaining bolts 3 Removethe TMAP 5 Install FTV to throttle body Mixer Inlet Fitting Throttle Cable FTV Bracket 1 f y throttle Cable ig Connection Throttl
243. o to Step 27 System OK 4 3 liter Emission Certified GM Engine Go to Step 26 SECTION 1B4 SYSTEM DIAGNOSIS IMPCO Technologies Engine Service Manual 1 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine LPG SYMPTOM DIAGNOSIS Symptom Diagnosis Important Preliminary Checks Before Using This Section Before using this section you should have performed On Board Diagnostic Check and determined that 1 The Control Module and MIL Malfunction Indicator Lamp are operating correctly 2 There are no Diagnostic Trouble Codes DTCs stored or aDTC exists but without a MIL Several of the following symptom procedures call for a careful visual and physical check The visual and physical checks are very important The checks can lead to correcting a problem without further checks that may save valuable time LPG Fuel System Check Verify the customer complaint Locate the correct symptom table Check the items indicated under that symptom Operate the vehicle under the conditions the symptom occurs Verify HEGO switching between lean and rich IMPORTANT Normal HEGO switching indicates the LPG fuel system is in closed loop and operating correctly at that time If a scan tool is available take a snapshot under the condition that the symptom occurs Go to Engine Scan Tool Data List to verify normal sensor values and parameters Visual and Physical Checks Check all ECM system fuses and circuit breakers
244. oid Additional Check Check for Electromagnetic Interference EMI EMI on the reference circuit can cause a missing condition Monitoring the engine RPM with a scan tool can detect an EMI A sudden increase in the RPM with little change in the actual engine RPM indicates EMI is present If the problem exists check the routing of the secondary wires and the ground circuit 8 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Hesitation Sag Stumble Po Checks Ati gt gt OE DEFINITION The vehicle has a momentary lack of response when depressing the accelerator The condition can occur at any vehicle speed The condition may cause the engine to stall if its severe enough Preliminary Checks Refer to Important Preliminary Checks Fuel System Checks Check the fuel pressure Refer to LPG Fuel System Diagnosis Check for low fuel pressure during a moderate or full throttle acceleration If the fuel pressure drops below specification there is possibly a faulty low pressure regulator or a restriction in the fuel system Check the Manifold Absolute Pressure MAP sensor response and accuracy Check LPL electrical connection Check the mixer air valve for sticking or binding Check the mixer module assembly for proper installation and leakage Check the PTV and FTV Ignition System Checks Note LPG being a gaseous fuel requires higher secondary ignition system voltage
245. ok similar but are serviced differently TWISTED LEADS SEE DOK LOCATE DAMAGED WIRE 2 REMOVE INSULATION AS REQUIRED SPLICE AND SOLDER 3 SPLICE TWO WIRE TOGETHER USING SPLICE CLIPS AND ROSIN CORE SOLDER SE 4 COVER SPLICE WITH TAPE TO INSULATE FROM OTHER WIRES 5 RETWIST AS BEFORE AND TAPE WITH ELECTRICAL TAPE AND HOLD iN PLA FIGURE 1 WIRE HARNESS REPAIR 2 IMPCO Technologies Engine Service Manual Micro Pack Refer to Figure 2 and repair procedure for replacement of a Micro Pack terminal 1 CABLE 3 LOCKING TANG 2 TERMINAL 4 TOOL J33095 BT8234 A FIGURE 2 MICRO PACK CONNECTOR Metri Pack Some connectors use terminals called Metri Pack Series 150 Figure 3 These may be used at the coolant sensor as well as TBI units They are also called Pull To Seat terminals because to install a terminal on a wire the wire is first inserted through the seal 5 and connector 4 The terminal is then crimped on the wire and the terminal pulled back into the connector to seat it in place To remove a terminal 1 Slide the seal back on the wire 2 Insert tool 3 BT 8518 or J 35689 or equivalent as shown in insert A and B to release the terminal locking tab 2 3 Push the wire and terminal out through the connector If reusing the terminal reshape the locking tang 2 Lo o 4 1 METRI PACK SERIES 150 FEMALE TERMINAL 2 LOCKING TA
246. old gaskets Sticking or leaking valves Exhaust system leakage e Check the intake and exhaust system for casting flash or other restrictions Fuel System Checks e Perform a fuel system diagnosis Refer to Gasoline Fuel System Diagnosis 24 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Lack of Power Sluggishness or Sponginess DEFINITION The engine delivers less than expected power There is little or no increase in speed when partially applying the accelerator pedal Preliminary Checks Refer to Important Preliminary Checks Refer to the Gasoline Fuel system Diagnostics Compare the customer s vehicle with a similar unit Make sure the customer has an actual problem Remove the air filter and check for dirt or restriction Check the vehicle transmission Refer to the OEM transmission diagnostics Fuel System Checks Check for a restricted fuel filter contaminated fuel or improper fuel pressure Refer to Gasoline Fuel System Diagnosis Check for the proper ignition output voltage with the spark tester J 26792 or the equivalent Check for fuel pump electrical circuit Verify proper fuel pump pressure Verify proper Fuel rail pressure Refer to the Gasoline Fuel System Diagnosis Check Electrical connections at the injectors Sensor Checks Check the Heated Exhaust Gas Oxygen Sensor HEGO for contamination and performance Check for proper operation ofthe MA
247. oline fuel system is in closed loop and operating correctly at that time If a scan tool is available take a snapshot under the condition that Mis symptom occurs Go e ngmg Scan Tool Data List to verify normal Visual and Physical Checks Check all ECM system fuses and circuit breakers Check the ECM ground for being clean tight and in its proper location Check the vacuum hoses for splits kinks and proper connections Check thoroughly for any type of leak or restriction Check for air leaks at all the mounting areas of the intake manifold sealing surfaces Check for proper installation of the Throttle Body assembly Check for fuel leaks at the fuel rail and injectors Check the ignition wires for the following conditions Cracking Hardness Proper routing Carbon tracking Check the wiring for the following items Proper connections pinches or cuts The following symptom tables contain groups of possible causes for each symptom The order of these procedures is not important If the scan tool readings do not indicate the problems then proceed in a logical order fi 16 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Intermittent DEFINITION The problem may or may not turn ON the Malfunction Indicator Lamp MIL or store a Diagnostic Trouble Code DTC Preliminary Checks Faulty Electrical Connections or Wiring Operational Test Intermittent Malfun
248. olt normally closed solenoid valve During closed loop operation the ECM sends a pulse signal to the FTV to open to allow more or less fuel to be introduced below the throttle blade to correct the air fuel mix ture for proper emission control Foot Pedal Position Sensor Throttle Position Sensor 9 Motor Figure 8 Throttle control device LPG Drive by cable throttle body assembly 6 IMPCO Technologies Engine Service Manual THREE WAY CATALYTIC MUFFLER The emission certified engine has been designed and calibrat ed to meet the emission standards in effect for 2004 To help meet the emission requirements the vehicle has been equipped with a Three Way Catalytic TWC muffler The catalyst muffler is a three way catalyst sound damping and spark ar resting unit Besides controlling the noise created from the combustion process and preventing sparks from escaping from the exhaust system the most important function is treat ing the exhaust gases which are created from the combustion process The three way catalyst consists of a honeycomb coated with a mixture of platinum palladium and rhodium The hot gases flow through the catalyst sections where an oxi dation and reduction reactions take place These chemical re actions reduce the amount of CO HC and NOX in the engines exhaust The exhaust gas then flows through the outlet Figure 9 Three way catalytic converter ENGINE CONTROL MODULE To obtain maximum effect from the
249. om the cylinder that indicates a misfire Refer to Spark Plug Wire Replacement 625 3 Measure the resistance of the spark plug wire with DMM Is the resistance less than the specified value Go to Step 16 Go to Step 15 1 Remove the spark plug from the cylinder that indicates a misfire Refer to Spark Plug Replacement Important If the spark plug is gas coolant or oil fouled determine the cause of the fouling Refer to DTC P0172 or P0175 for spark plugs that are gas fouled Refer to Symptoms Engine Mechanical 4 3L for spark plugs that are coolant or oil fouled 2 Inspect the spark plug Refer to Spark Plug Inspection Did you find and correct the condition Go to Step 17 Go to Step 10 18 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 DTC P0300 cont d Exchange the suspected spark plug with another cylinder that is operating correctly Start the engine Operate the engine within the conditions that the misfire occurred Monitor the Misfire Current Counters with a scan tool Did the misfire move with the spark plug Go to Step 14 Go to Step 11 Important Ensure that all the injectors operate High resistance in an injector circuit causes the injector to be inoperative without setting a fuel injector DTC Return to this diagnostic after you complete the Fuel Injector Coil Test Perform the Fuel Injector Coil Test Refer to Fuel Injector Coil Tes
250. on Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM has checks that must be satisfied each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 120 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 511 COP Failure Ye No 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code Does 511 reset with the engine idling 3 e Checkall ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electri
251. onnect the fuel return line 15 Connect the fuel supply line 16 Install the throttle body assembly Refer to Throttle Body Assembly Replacement 17 Install the air duct 18 Connect the negative battery cable 19 Start engine 20 Install diagnostic tool and check for DTC codes or MIL lights INJECTOR REPLACEMENT Figure 7 1 Disconnect the negative battery cable 2 Relieve the fuel system pressure Refer to Gasoline Fuel System Pressure Relief 3 Remove the fuel rail assembly Refer to Fuel Rail Replacement 4 Disconnect the six 6 injector electrical connections Remove each injector Installation Procedure IMPORTANT e Apply a small amount of o ring lubricant to the in jector o rings before installation e Lightly Lubricate the o ring of the throttle body as sembly and the inlet o ring on each injector e Cover Throttle body adapter opening and injectors to prevent debris from entering engine or the injec tors until reassembly 5 Install the injectors 6 Connect the injector electrical connectors 7 Reinstall the fuel rail assembly Refer to Fuel Rail Replacement 8 Start engine and check for leaks Fuel System 1E1 9 Install diagnostic service tool and verify engine is oper ating closed loop and no MIL light is present TEMPERATURE MANIFOLD ABSOLUTE PRESSURE REPLACEMENT Figure 7 1 Disconnect the TMAP electrical connection 2 Remove the one 1 retaining bolt and retain 3 Remove the TMAP I
252. onnected in problem System Data Mode Go to Intermittent e Warm Engine to normal operating temperature socion then run the engine above 650 rpm for 60 seconds Does DST display ECT temperature of 230 degrees F or greater with the engine running over 650 rpm e Verify with a temperature gauge that the engine Repair Cooling Go to step 4 coolant is over 225 degrees F system Does the temperature gauge indicate 225 degrees F or greater Verify ECT circuit function Follow diagnostic test procedure for DTC 122 ECT Low Voltage IMPCO Technologies Engine Service Manual 45 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 124 ECT Higher Than Expected 2 Sensor Ground Conditions for Setting the DTC Engine Coolant Temperature Check Condition Engine Running Fault Condition Engine Coolant temperature reading or estimate greater than 250 deg and engine RPM greater than 650 MIL On for active fault and for 15 seconds after active fault Adaptive Enabled Closed Loop Enabled and allowed to stay at limit will still set limit fault 9 Engine Shut Down Circuit Description 46 The Engine Coolant Temperature sensor is a thermistor temperature sensitive resistor located in the engine coolant The ECT Engine Coolant Temperature sensor that is located in the coolant near the thermostat The ECT is used for engine airflow calculation ignition timing control fu
253. ons in the system are identified by a Diagnostic Code number In addition to notifying the operator of the malfunction in the system the controller also stores the information about the malfunction in its memory A technician can than utilize a computerized di agnostic tool to retrieve the stored diagnostic code and by us ing the diagnostic charts in this manual determine the cause ofthe malfunction In the event a technician does not have the computerized diagnostic tool the MIL light can be used to identify the diagnostic code By following specific steps the technician can activate the 4 3 liter Emission Certified GM Engine Fuel System Operation 1A2 GASOLINE ECM INPUTS 02 Sensor 3 Throttle Position 3 RPM Timing 2 Oil Pressure Coolant Temperature gt Air Temperature Manifold Absolute Pressure Battery ENGINE CONTROL MODULE OUTPUTS Gasoline Fuel Pump Governor Speed Control Gasoline Fuel Injector Timing Ignition Gauges Malfunction Indicator Lamp Figure 5 Gasoline Engine Control Module ECM blink feature and count the number of blinks to determine the diagnostic code number to locate the fault in the system HEATED EXHAUST GAS OXYGEN SENSOR The Heated Exhaust Gas Oxygen Sensor HEGO
254. onsists of the following circuits The 12 volt reference circuit The low reference circuit The sensor signal circuit Conditions for Running the DTC The control module turns OFF the malfunction DTCs P0101 P0102 P0103 or P0341 are indicator lamp MIL after 3 consecutive ignition not set cycles that the diagnostic runs and does not fail The camshaft position sensor CMP is A current DTC Last Test Failed clears when the transitioning diagnostic runs and passes The mass airflow MAF is more than 3 g s in history clears after 40 consecutive warm up Crank mode cycles if no failures are reported by this or any other emission related diagnostic Clear the MIL and the DTC with a scan tool The is more than 5 0 5 in Run mode Conditions for Setting the DTC The CKP sensor signal is not detected for more than Test Description 3 seconds The numbers below refer to the step numbers on the Sine diagnostic table 2 This step determines if the DTC P0336 is an intermittent This step checks the ignition 1 voltage circuit to the crankshaft position sensor 4 This step checks the crankshaft position sensor low reference circuit Action Taken When the DTC Sets The control module illuminates the malfunction 3 indicator lamp MIL on the second consecutive ignition cycle that the diagnostic runs and fails The control module records the operating conditions at
255. ools shown in this service manaual that have tool product numbers begin ning with J or BT are available for world wide distribution from o Kent Moore Tools o 28635 Mound Road o Warren MI 48092 o 1 800 345 2233 Special Tools which are required to service the LPG fuel system are listed below o Hand held diagnostic scanner o Fuel pressure test kit The tools are available from IMPCO Engine System Division 7100 East 15 Mile Road Sterling Heights MI 48312 1 586 276 4333 ENGLISH AND METRIC FASTENERS Late model engines use a combination of English and Metric fasteners The components affected are the starter motor engine mounts and flywheel housing mounting Other components may also have a combination of fas teners always verify that the proper fasteners are used whenever removing or replacing any components 4 3 liter Emission Certified GM Engine General Information OA Air Valve Vacuum The vacuum signal taken from below the air valve assembly and above the throttle butterfly ADP Adaptive Digital Processor Air Fuel Ratio The amount of air and fuel in the air fuel mixture which enters the engine shown in a ratio Analog Voltmeter A meter that uses a needle to point to a value on a scale of numbers usually of the low impedance type used to measure voltage and resistance Aromatics Pertaining to or containing the six carbon ring characteristic of the benzene series Fo
256. oop Enabled Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and Adaptive multiplier This fault will set if the adaptive multiplier exceeds the limits of normal operation Diagnostic Aids If any other DTCs are present diagnose those first Oxygen Sensor Wire Heated Oxygen sensor wires may be mis routed and contacting the exhaust manifold Vacuum Leaks Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at especially at light load Injectors System will be lean if an injector driver or driver circuit fails open The system will also be lean if an injector fails in a closed manner or is dirty Fuel Pressure Low fuel pressure faulty fuel injector or damaged fuel pump assembly can cause fuel system to run lean Exhaust Leaks If there is an exhaust leak outside air can be pulled into the exhaust and past the 02 sensor causing a false lean condition Fuel Guality Contaminated or spoiled fuel can cause the fuel system to be lean Ground Problem ECM grounds must be good battery or engine ground 110 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 243 Adaptive Learn High LPG Value s Yes No e Perform the On Board OBD System Check Go to ET 3 Goto Step
257. operate normally with no stored codes IMPCO Technologies Engine Service Manual 71 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 135 BP Low Pressure Motorola TMAP TMAP SENSOR Conditions for Setting the DTC Barometric Pressure Check Condition Key On Fault Condition BP less than 8 3 psia MIL On for active fault and for 2 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The BP Barometric Pressure is estimated from the TMAP sensor The barometric pressure value is used for fuel and airflow calculations This fault sets in the event the BP value is out of the normal range 72 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 135 BP Low Pressure Motorola Step JJ Aces Ye Wo Did you perform the On Board OBD System Check Go to ies 2 Go to OBD System Check Section Go to Step 3 Intermittent e Key On problem e DST Diagnostic Scan Tool connected in System Data Mode Go to Intermittent section Go to Step 4 Go to step 8 Does DST display BP pressure of 8 3 psia or less Key OFF Disconnect the TMAP sensor from the wiring harness Jumper the 5 volt reference pin C and MAP signal pin D together Key ON Does the DST display BP pressure of 16 00 psia or greater e Key OFF e Disconnect ECM
258. or a long time The engine does eventually run or may start but immediately dies Preliminary Checks e Refer to Important Preliminary Checks e Make sure the vehicle s operator is using the correct starting procedure Sensor Checks e Check the Engine Coolant Temperature sensor with the scan tool Compare the engine coolant temperature with the ambient air temperature on a cold engine IF the coolant temperature reading is more than 5 degrees greater or less than the ambient air temperature on cold engine check for high resistance in the coolant sensor circuit Refer to DTC 111 e Check the Crankshaft Position sensor e Check the Throttle position TPS and Foot Pedal Position FPP sensor Fuel System Checks Important A closed LPG manual fuel shut off valve will create an extended crank OR no start condition Verify the excess flow valve in LPG manual shut off valve is not tripped Check mixer module assembly for proper installation and leakage Verify proper operation of the low pressure lock off solenoids Verify proper operation ofthe PTV and Check for air intake system leakage between the mixer and the throttle body Check the fuel system pressures Refer to the Fuel System Diagnosis Ignition System Checks Note LPG being a gaseous fuel requires higher secondary ignition system voltages for the equivalent gasoline operating conditions Check for the proper ignition voltage output with J 26792 or the
259. or more conductors at a single point Stoichiometric Ratio An ideal fuel air ratio for combustion in which all ofthe fuel and most ofthe oxygen will be burned Sulfur Oxides Chemical compounds where sulfur is bonded to varying numbers of oxygens produced by the combustion of gasoline or any other fuel that contains sulfur As sulfur oxides decompose in the atmosphere they combine with water to form sulfuric acid System Pressure The fuel pressure maintained in the system during normal engine operation Tap An electrical term for a type of splice where the original circuit is not interrupted TBI Throttle Body Injection Any of several injection systems that have the fuel injector s mounted in a centrally located throt tle body Throttle Body Controls engine RPM by adjusting the engine manifold vacuum to the mixer Consists of housing shaft throttle liner and butterfly valve TLEV Transitional Low Emission Vehicle TMAP Combined Air Inlet and Manifold Pressure Sensor Toluene A liquid aromatic hydrocarbon C7H8 TPS Throttle Position Sensor ULEV Ultra Low Emission Vehicle Vaporization process in which liquid changes states into gas Venturi Air Valve Vacuum VAV V An amplified air valve vacuum signal coming from the venturi area of the mixer directly exposed to airflow before the addition of vaporized LPG Volt Ohmmeter VOM A combination meter used to measure voltage and resistance in an electrical circuit Availa
260. ormance and driveability After operating the engine within the test parameters of DTC 632 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 155 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 637 Throttle Unable To Open PNK WHT DBW 24 C ror m TPS1 PPL LT BLU TPS 1 Signal X 53 g BLK LT GRN Sensor Ground FPP DK BLU FPP Signal C 38 5 VOLTS ECM Conditions for Setting the DTC Throttle Position Sensor Check Condition Cranking or Running Fault Condition Throttle command is 20 more than actual throttle position MIL On during active fault Adaptive Enabled Closed Loop Enabled 9 Engine Shut Down Circuit Description 156 There are 2 Throttle Position Sensors located within the throttle which use variable resistors to determine signal voltage based on throttle plate position TPS1 will read low voltage when closed and TPS2 will read high voltage when closed The TPS1 and TPS2 percentages are calculated from these voltages Although the voltages are different the calculated values for the throttle position percentages should be very close to the same The TPS values are used by the ECM to determine if the throttle is opening as commanded This fault will set if the throttle command is 2096 or more than the actual throttle position During this active fault the MIL light will
261. ory if the does not reset within 50 consecutive engine run cycles While a Diagnostic Trouble Code is current for a sensor the ECM may assign a default limp home value and use that value in its control algorithms of the system diagnostic self tests run continuously during normal vehicle operation IMPCO Technologies Engine Service Manual 11 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine OBD SYSTEM CHECK MALFUNCTION INDICATOR LAMP MIL co22 Co F LT BLUE BLK Hot in Start and Run Circuit Description The Spectrum Fuel system is equipped with OBD On Board Diagnostics The system has a dash mounted MIL Malfunction Indicator Lamp for the indication of system problems Engine control system problems that affect emissions or driveability of the vehicle will set a DTC Diagnostic Trouble Code The ECM will then provide a path to ground and illuminate the MIL Malfunction Indicator Lamp The MIL has the following functions 1 It notifies the driver of a problem with the fuel system ignition system or emission control system so the driver can arrange for service as soon as possible 2 It will display DTC s that have been stored due to a system malfunction The lamp should illuminate when the key is in the ON position and the engine is not running This feature verifies that the lamp is in proper working order If the lamp does not come on with the vehicl
262. osed Loop Enabled Engine Shut Down Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The IAT is a calculated value based mainly on the IAT sensor at high airflow and influenced more by the ECT Engine Coolant Temperature at low airflow This fault will set ifthe Intake Air Temperature is greater than 220 degrees F and engine RPM is greater than 1000 The MIL light will be on during this active fault and the engine will shut down 30 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 114 IAT Higher Than Expected 2 Bosch TMAP Diagnostic Aids This fault will set when inlet air is much hotter than normal The most common cause of high inlet air temperature is a problem with the inlet air system Ensure that the air inlet is not obstructed modified or damaged Inspect the air inlet system for cracks or breaks that may allow unwanted under hood air in to the air inlet system If none of the above can be found Follow the diagnostic steps
263. ous fuel requires higher secondary ignition system voltages for the equivalent gasoline operating conditions Check for the proper ignition voltage output with J 26792 or the equivalent that spark plugs are correct for use with LPG R42LTS Check the spark plugs for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Check for bare or shorted ignition wires Check for loose ignition coil connections at the coil 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Engine Mechanical Checks Exhaust System Checks Important The LPG Fuel system works on a fumigation principle of fuel introduction and is more sensitive to intake manifold leakage than the gasoline fuel supply system e Check for the following Vacuum leaks Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes Check the exhaust system for a possible restriction Inspect the exhaust system for damaged or collapsed pipes Inspect the muffler for signs of heat distress or for possible internal failure Check for possible plugged catalytic converter Refer to Restricted Exhaust System Diagnosis IMPCO Technologies Engine Service Manual 5 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Hard Start DEFINITION The engine cranks OK but does not start f
264. ove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 243 check for any stored codes Does the engine operate normally with no stored codes 112 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 113 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 244 Adaptive Learn Low LPG fam Sensor Sensor Ground Heater To System Power Relay To Engine Ground Conditions for Setting the DTC Heated Oxygen Sensor Check Condition Engine running Fault Condition Adaptive multiplier out of range at limit of 30 MIL Disabled Adaptive Enabled Closed Loop Enabled Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and Adaptive multiplier This fault will set if th
265. ow Emission Vehicle IMPCO Imperial Machine Products Company IMPCO Technologies Inc A manufacturer of both LPG and Gasoline fuel sys tems Impedance A form of opposition of AC current flow resistance measured in ohms Insulation A nonconductive material used to cover wires in electrical circuits to prevent the leakage of electricity and to protect the wire from corrosion Intercept An electrical term for a type of splice where the original circuit is interrupted and redirected through another circuit ITK IMPCO Test Kit Knock Sound produced when an engine s air fuel mixture is ignited by something other than the spark plug such as a hot spot in the combustion chamber Can be caused by a fuel with an octane rating that is too low or maladjusted ignition timing Also called detonation or ping Lambda Sensor A feedback device usually located in the exhaust manifold which detects the amount of oxygen present in ex haust gases in relation to the surrounding atmosphere LDV Light Duty Vehicle 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine General Information OA Lean Mixture An air to fuel ratio above the stoichiometric ratio too much air LEV Low Emission Vehicle Limp in or Limp home This term is used to describe the drivability characteristics of a failed computer system Liquified Petroleum Gas LPG A fuel commonly known as propane consisting mostly of propane C3H8 derived
266. ow appear and a green banner in the upper left hand will read Connected 4 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DIAGNOSTIC TROUBLE CODES EDIS ECI Serial Communications 181 File Page Flash Comm Plot Log Help Link error attempting reconnect m Toggle Page F8 Faults Controls Inc Connected at 19200 bps Alas Control and instrumentation Specialist _Toggle Test Cell F10 Fauft Access MIL System States DBW Vanables Ka ER Er less Do leteti Engine Speed 1400 Run Mode Running _ TPS command 00 x fing order pe i GES wes Manifold Pressure psia Fuel Type Gasoline TPS position 01 X 1 424 1 o2f mo Coolant Temperature 1950 degF FuelContolMode CLAcie FPP command 00 X 2 2 of 15 Cylinder Head Temp 1950 degF Govemor switch state 5073 position 00 X oo off 145 Manifold Temperature 1075 degF Active governor type Min TPS1 voltage 0484 vols o 15 Intake Air Temperature 1057 degF Active govemor mode Droop TPS2 voltage 4477 volts 5 oof oo Vbat 139 volts Brake input level Open FPP1 voltage 0442 volts 6 oof 00 vw 137 vols Oil pressure state OK FPP2 voltage 0 000 volts Hour meter 2843 hous IVS voltage 5000 vols Cumulative starts 13 starts Closed Loop Digital input Voltages Diagnostic Modes 1 0582 vots Fu
267. oxygen sensors indicate a lean condition fuel trim values will be above 0 percent If the oxygen sensors indicate a rich condition fuel trim values will be below percent Short Term fuel trim values change rapidly in response to the heated oxygen sensor HO2S voltage signals Long Term fuel trim makes coarse adjustments in order to maintain Air Fuel Ratio of 14 7 1 If the PCM detects an excessively lean condition this DTC will set Conditions for Running the DTC DTCs P0101 P0103 P0108 P0135 P0137 P0141 P0200 P0300 P0410 P0420 P0430 P0440 P0442 P0443 P0446 P0449 P0506 P0507 or P1441 are not set The engine coolant temperature ECT is between 75 115 C 167 239 F The intake air temperature IAT is between 20 to 90 C 4 194 F The manifold absolute pressure MAP is between 26 90 kPa 3 7 13 psi The vehicle speed is less than 137 km h 85 mph The engine speed is between 400 3 000 The barometric pressure BARO is more than 74 kPa 10 7 psi e The mass airflow MAF is between 5 90 g s The fuel level is more than 10 percent The throttle position is less than 90 percent Conditions for Setting the DTC The average long term fuel trim cell value 15 above 23 percent All of the above conditions are present for 6 seconds SIO ID 727820 Action Taken When the DTC Sets The control module illuminates the malfunction indicator lamp M
268. p 5 connector terminals for corrosion contamination circuit as or mechanical damage necessary Any problems found Refer to Wiring Repairs in Engine o to Step Repair the Disconnect ECM connector circuit as Check for continuity between TMAP sensor necessary connector pin 4 and ECM connector pin 33 Refer to Do you have continuity between them wen in Engine y o to step 7 Repair the connector 5 volt supply pin 3 and ECM connector circuit as pin 50 necessary Do you have continuity between them Refer to Wiring Repairs in Engine DST Diagnostic Scan Tool connected in System Data Mode between o to step 1 the connector ground pin 1 and ECM connector pin circuit as 49 necessary Do you have continuity between them Refer to Wiring Repairs in Engine Electrical emove Jumper that was installed during step o to Step 9 1 step e Probe TMAP connector signal circuit pin 4 with a test light connected to battery voltage Does the DST display BP pressure of 16 00 psia or eater IMPCO Technologies Engine Service Manual 69 1 4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 70 K o to step 10 Repair the Disconnect ECM connector circuit as Check for continuity between TMAP sensor necessary connector pin 3 and ECM connector pin 50 Refer to Do you have continuity between them waning Rep ie in Engine y Repair the o to Step connector 5 volt referen
269. p Enabled Circuit description This fault will set anytime the engine RPM exceeds 3800 for 2 seconds or more continuously This speed overrides any higher max governor speeds programmed by the user This is to help prevent engine or eguipment damage The MIL will be on during this active fault 164 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 651 Max Govern Speed Override vau Ye mo 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section e Key ON Engine OFF Go to Step 3 Go to Step 4 e DSTin Active Fault Mode mE Are any other DTC codes present with DTC 651 Go to Step 6 Go to Step 5 Go to Step 8 Go to Step 7 e Diagnose any other DTC codes before proceeding with this chart Have any other DTC codes been diagnosed and repaired 4 e Checkthe Service Part Number on the ECM to ensure correct calibration is in use Is the Service Part Number Correct 5 e Replace ECM with correct Service Part Number Is the replacement complete e Check the mechanical operation of the throttle Is the mechanical operation of the throttle OK e Check engine for large manifold vacuum leaks Refer to Fuel Systems Section 1B Symptom Diagnostics Go to Step 9 Go to OBD System Check Section System OK Go to OBD System Check IMPCO Technologies Engine Service Manual 165 Did you find and correct th
270. perature reading or estimate greater than 240 deg and engine RPM greater than 650 MIL Will flash at 2 Hz twice per second during active fault Adaptive Disabled during active fault Closed Loop Enabled and allowed to stay at limit will still set limit fault Power Derate levell Circuit Description 44 The Engine Coolant Temperature sensor is a thermistor temperature sensitive resistor located in the engine coolant The ECT Engine Coolant Temperature sensor that is located in the coolant near the thermostat The ECT is used for engine airflow calculation fuel enrichment ignition timing control to enable certain features and for engine protection The ECM provides a voltage divider circuit so when the sensor reading is cool the sensor reads higher voltage and lower when warm This fault will help protect the engine in the event of over temperature When the coolant exceeds 240 degrees F and engine RPM exceeds 650 this fault will set and Power Derate 1 will be enforced During this fault maximum throttle position is 5096 and the MIL light will flash twice per second IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 123 ECT HIGHER THAN EXPECTED 1 Value s Ye No Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 e Key On Go to Step 3 Intermittent DST Diagnostic Scan Tool c
271. pressure to approximately negative 38 1 mm 1 5 of wa ter column The fuel is then drawn from the secondary chamber of the LPR by the vacuum generated by air flowing through the mixer This vacuum signal is also used to generate lift for the mixer air valve This vacuum signal is most commonly referred to as air valve vacuum In the mixer the fuel mixes with the air entering the engine This air fuel mixture is then drawn into the engine for combustion Diagnostic Aids This procedure is intended to diagnose a vehicle operating on LPG If the vehicle will not continue to run on LPG refer to Hard Start for preliminary checks Before proceeding with 2 IMPCO Technologies Engine Service Manual this procedure verify that the vehicle has a sufficient quan tity of fuel and that liquid fuel is being delivered to the LPR Also ensure that the manual shut off valve on the LPG tank is fully opened and that the excess flow valve has not been activated Tools Required 7 16 Open end wrench for test port plugs Straight Blade screw driver e DVOM GM J 39200 Fluke 88 or equivalent Duty Cycle Monitoring Tool IMPCO Fuel System Analyzer FSA or DVOM GM J 39200 Fluke 88 or equivalent Diagnostic Scan Tool IMPCO hand held Diagnostic Scan Tool DST Pressure Gauges Water Column Gauge Manometer GM 7333 6 or equivalent 0 10 PSI Gauge Test Description The numbers below refer to step numbers on the diag
272. properly remove the motor and refer to Starter Motor Disassembly Test and Assembly procedures in the appropriate Section Never operate the starter motor more than 30 seconds at a time without pausing to allow it to cool for at least 2 minutes Overheating caused by excessive cranking seriously damages the starer motor IMPCO Technologies Engine Service Manual 1 1C5 Starter 4 3 liter Emission Certified GM Engine STARTER MOTOR NOISE DIAGNOSIS CHART PROBLEM POSSIBLE CAUSE CORRECTION High pitched whine during Distance too great between the starter Remove shims at the starter mount if cranking before engine fires pinion and the flywheel installed Refer to Starter Motor but engine cranks and fires Noise in this section normally High pitched whine after the Distance too small between the starter Add shims at the starter mount Refer engine fires as key is being pinion and the flywheel Flywheel to Starter Motor Noise in this released The engine cranks runout contributes to the intermittent section and fires normally This nature of the problem complaint is often diagnosed as starter hang in or solenoid weak A loud whoop after the engine Usually due to a worn starter motor Remove the starter motor and check fires but while the starter is still clutch the clutch held engaged Sounds like a siren if the engine is revved while the starter is engaged A rumble growl or in Usua
273. provides feed back to the ECM on the amount of oxygen present in the ex haust stream after combustion The measurement of oxygen in the exhaust stream is measured in voltage and sent to the ECM The ECM then makes corrections to the fuel air ratio to ensure the proper fuel charge and optimum catalytic per formance Therefore it is important that the exhaust connec tions remain secured and air tight IMPORTANT The EGO sensor is sensitive to silicone or silicone based products Do not use silicone sprays or hoses which are as sembled using silicone lubricants Silicone contamination can cause severe damage to the EGO When inspecting the Exhaust system check the following Check the exhaust manifold at the cylinder head for leaks and that all retain bolts and shields if used are in place Check the manifold to exhaust pipe fasteners to ensure they are tight and that there are no exhaust leaks repair if necessary Check EGO electrical connector to ensure connector is seated and locked check wires to ensure there is no cracking splits chaffing or burn through repair if nec essary 8 IMPCO Technologies Engine Service Manual Check any exhaust pipe extension connector for leaks tighten if necessary Visually inspect converter to insure muffler is securely mounted and tail pipe is properly aimed Check for any leaks at the inlet and outlet of the convert er 4 3 liter Emission Certified GM Engine Maintena
274. r Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 122 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 512 invalid Interrupt Value s Yes mo 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code section Does DTC 512 reset with the engine idling 3 e Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical e Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 512 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies
275. r screw and tighten Figure 4 12 1 Disconnect battery cables from battery 5 Connect solenoid wires and battery cables 2 Disconnect wires from solenoid terminals 3 Remove screw from field coil connector and solenoid attaching screws figure 4 12 4 Twist solenoid to disengage tab and remove SERVICEABLE SEALED SOLENOID TOTALLY ENCLOSED SHIFT MECHANISM SHUNTED 0 2222252225 a ROLLER BEARING PERMANENT MAGNET FIELD 9 TI lt a EN L y mmm HIGH CAPACITY OVERRUNNING DRIVER HIGH SPEED PLANETARY GEAR RADIAL SPRING BALANCED ARMATURE REDUCTION ASSEMBLY ASSEMBLY 7226 200 001A Figure 4 14 Cross Section of PG260 Starter Motor IMPCO Technologies Engine Service Manual 1 1C5 Starter SOLENOID SWITCH TESTING Figure 4 13 1 Using continuity meter connect test leads as shown in figure 4 13 and connect 12 volt battery with jumper leads 2 If no meter movement is present replace solenoid PG260 STARTER MOTOR IDENTIFICATION Figure 4 14 The PG260 starter motor can easily be identified by the 3 Torx bolts that retain the solenoid to the drive end housing The starter motor features small permanent magnets mounted inside the field frame A permanent magnet motor is about half the weight and size of a field coil motor having the same crank ing performance The drive housing encloses the shift lever the shift lever mechanism and th
276. r the circuit as necessary Refer to Wiring Repairs in r open circuit as necessary Refer to Wiring Repairs in Engine voltage source Refer to OEM body and chassis wiring o to Step open circuit as necessary Refer to Section 1C2 for wiring repairs IMPCO Technologies Engine Service Manual 13 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 111 IAT High Voltage Bosch TMAP SENSOR Conditions for Setting the DTC Intake Air Temperature Check Condition Engine Running Fault Condition IAT Sensor Voltage greater than 4 95 MIL On during active fault and for 2 seconds after active fault Adaptive Disabled during active fault Closed Loop Enabled Circuit Description The TMAP is a combined IAT Intake Air Temperature and MAP Manifold Absolute Pressure sensor A temperature sensitive resistor is used in the TMAP located in the intake manifold of the engine It is used to monitor incoming air temperature and the output in conjunction with other sensors is used to determine the airflow to the engine The ECM provides a voltage divider circuit so that when the air is cool the signal reads higher voltage and lower when warm The is a calculated value based mainly on the sensor at high airflow and influenced more by the Engine Coolant Temperature at low airflow This fault will set if the signal voltage is more than 4 95 volts anytime the engine is ru
277. red codes 144 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 145 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 612 FPP Low Voltage LT GRN RED 5 volts DK BLUE BLK LT GREEN Sensor Ground Conditions for Setting the DTC Foot Pedal Position Check Condition Key On Fault Condition FPP sensor voltage less than 0 2 MIL On during active fault and flashing at 2 Hz twice per second after active fault for the remainder of the key on cycle Adaptive Enabled Closed Loop Enabled Power Derate level 1 and Low Rev Limit enforced Circuit Description The Foot Pedal Position sensor uses a variable resistor to determine signal voltage based on pedal position Less depression of pedal results in lower voltage and greater depression results in higher voltage This fault will set if voltage is less than 0 2 volts at any operating condition while the key is on Ifthe voltage is less than 0 2 then FPP is considered to be out of specifications At this point the ECM does not have a valid signal and must therefore enforce the low rev limit and Power Derate level 1 When these are enforced the maximum throttle position is 50 and the maximum engine speed is 1600 RPM The low rev limit is enforced for the remainder of the key on cycle If the active fault is no longer present the MIL light wi
278. rform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to Step 3 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical e Key On Engine OFF 5 0 volts Go to Step 4 Repair the circuit e Disconnect the Crankshaft position Sensor as necessary connector C009 Refer to Wiring e Using A DVOM check for voltage at the sensor Repairs in Engine connector pin A and engine ground Electrical Do you have voltage Key OFF Go to Step 5 Repair the circuit Disconnect ECM connector C001 Using aDVOM check for continuity between Refer Wiring Repairs in Engine Electrical Go to Step 6 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to Step 7 as necessary Refer to Wiring Repairs in Engine Electrical connector pin B and ECM connector pin 12 Do you have continuity between them Repair the circuit Go to step 8 as necessary Refer to Wiring Repairs in Engine Electrical m mE Go to Step 11 e Check that the ECM ground terminals G1 and G2 are clean and tight Are the ground terminals G1 and G2 clean and tight connector pin C and ECM connector pin 11 Do you have continuity between them e Inspect the connector C009 terminals for damage corrosion or contamination Did you find a problem e Inspect the ECM connector C001 terminals 11 12 and 50 for d
279. ription The numbers below refer to the step numbers on the diagnostic table The above conditions are present for a minimum of 2 5 seconds Action Taken When the DTC Sets The control module illuminates the malfunction indicator lamp MIL on the second consecutive ignition cycle that the diagnostic runs and fails The control module records the operating conditions at the time the diagnostic fails The first time the diagnostic fails the control module 2 Listen for a click when the fuel pump relay operates Command both the ON and OFF states Repeat commands as necessary 4 This step verifies that the PCM is providing voltage to the fuel pump relay 5 This step tests for an open in the ground circuit to the fuel pump relay 6 This step determines if voltage is constantly being applied to the control circuit of the fuel pump relay DTC P0230 seel o dion oo _ Schematic Reference Engine Controls Schematics Did you perform the Diagnostic System Check Engine Controls 1 Turn ON the ignition with the engine OFF Go to Diagnostic System Check Go to Step 2 Engine Controls 2 Command the fuel pump ON and OFF with a scan tool Does the fuel pump relay turn ON and OFF with each command Go to Step 3 Go to Step 4 Observe the Freeze Frame Failure Records data for this DTC Turn OFF the ignition for 30 seconds Start the engine Operate the vehicle within the Condition
280. roblem necessary Refer to Wiring Repairs in Engine Electrical 12 e Replace throttle Go to Step 13 Is the replacement complete IMPCO Technologies Engine Service Manual 161 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses System Check etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 638 check for any stored codes Does the engine operate normally with no stored codes 162 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 IMPCO Technologies Engine Service Manual 163 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 651 Max Govern Speed Override TAN ORN TPS1 PPL LT BLU TPS 1 Signal 4 BLK LT GRN Sensor Ground FPP FPP Signal LT GRN RED 5 VOLTS Conditions for Setting the DTC Max Govern Speed Override Check Condition Engine Running Fault Condition Engine RPM greater than 3800 for 2 seconds continuously MIL On during active fault Adaptive Enabled Closed Loo
281. s Check for the proper ignition voltage output with J 26792 or the equivalent Verify that the spark plugs are correct use R42LTS Check the spark plugs for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Check for bare or shorted ignition wires Check for loose ignition coil connections at the coil Engine Mechanical Checks Check for the following Vacuum leaks Improper valve timing Low compression Bent pushrods Worn rocker arms Broken or weak valve springs Worn camshaft lobes 18 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Exhaust System Checks e Check the exhaust system for a possible restriction Inspect exhaust system for damaged or collapsed pipes Inspect muffler for signs of heat distress or for possible internal failure e Check for possible plugged catalytic converter Refer to Restricted Exhaust System Diagnosis IMPCO Technologies Engine Service Manual 19 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Hard Start DEFINITION The engine cranks OK but does not start for a long time The engine does eventually run or may start but immediately dies Preliminary Checks e Refer to Important Preliminary Checks e Make sure the vehicle s operator is using the correct starting procedure Sensor Checks e Check the Engine Coolant Temperature sensor with the scan tool
282. s DBW testmode V Normal EGO2 soo 208 wh tees Overspeed voltage 50 volts Data SnapShot SnapShot Closeddoop 2 ox Inj 3 FO se Base Custom mna 5 Oil pressure voltage 50 volts Inj 4 FO tions Definitions Definitions Inj5 FO EMPTY Inj FO P run tm sec 7 Historic Faults Active Faults FPP pct em EMPTY 5_ EMPTY emi fer y O lem Jer Wwev cL evi EMPTY Fw avg CL BM2 EMPTY A BM1 A A BM2 A BM2 Flight Data FPF_pet Custom ITPS pct Definitions EGO volts EMPTY EGO2 volts EMPTY las o TRIM DC hours The Injector Kill mode is used to disable individual fuel injectors If the Injector Kill mode is selected with the engine running below 1000 RPM the minimum throttle command will lock into the position it was in when the test mode was entered If the Injector Kill mode is selected with the engine running above 1000 RPM the throttle will continue to operate normally Disabling Injectors To disable an injector use the mouse to select the desired The word Normal will change to the Injector you have selected The injector driver can be re enabled by selecting again If the engine is running below 1000 RPM the injector driver will stay disabled for 15 seconds and then re set Ifthe engine is running above 1000 RPM the injector driver will stay disabled for 5 seconds and then re set Record the change in rpm or close
283. s for Running the DTC as specified in the supporting text or as close to the Freeze Frame Failure Records data that you observed Does the DTC fail this ignition Go to ntermittent Go to Step 4 Conditions IMPCO Technologies Engine Service Manual 15 1C7 Ignition System 4 3 liter Emission Certified GM Engine DTC P0230 cont d Step ction 1 Turn OFF the ignition 2 Disconnect the fuel pump relay 3 Turn ON the ignition with the engine OFF 4 Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground 5 Command the fuel pump ON and OFF with a scan tool Does the test lamp turn ON and OFF with each command Go to Step5 Go to Step 6 1 Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the relay 2 Command the fuel pump ON and OFF with a scan tool Does the test lamp turn ON and OFF with each command Go to Step 9 Go to Step 11 6 Does the test lamp remain illuminated with each command Go to Step 8 Go to Step 7 Test the control circuit of the fuel pump relay for a short to ground or for an open Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition Go to Step 14 Go to Step 10 Test the control circuit of the fuel pump relay for a short to voltage Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition Go to Step 1
284. s for the equivalent gasoline operating conditions If a problem is reported on LPG and not gasoline do not discount the possibility of a LPG only ignition system failure and test the system accordingly Check for the proper ignition voltage output with J 26792 or the equivalent Verify that the spark plugs are correct for use with LPG R42LTS Check for faulty spark plug wires Check for fouled spark plugs Additional Check Check for manifold vacuum or air induction system leaks Check the generator output voltage IMPCO Technologies Engine Service Manual 9 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine Backfire DEFINITION The fuel ignites in the intake manifold or in the exhaust system making a loud popping noise Preliminary Check e Refer to Important Preliminary Checks Ignition System Checks Important LPG being a gaseous fuel requires higher secondary ignition system voltages for the equivalent gasoline operating conditions The ignition system must be maintained in peak condition to prevent backfire e Check for the proper ignition coil output voltage using the spark tester J26792 or the equivalent Check the spark plug wires by connecting an onmmeter to the ends of each wire in question Ifthe meter reads over 30 000 ohms replace the wires Check the connection at ignition coil Check for deteriorated spark plug wire insulation Check the spark plugs The correct spark plugs for LPG are R42LTS
285. s for the excessive back pressure the catalytic converter is suspected to be restricted and should be replaced using current recom mended procedures Fuel System 1E1 IMPCO Technologies Engine Service Manual 13
286. s for voltage at the fuel injector harness connector The ECM 1 fuse supplies power to the coil side of the fuel injector harness connector If the fuse is open a short to ground on the ignition 1 voltage supply circuit of the fuel injector is indicated 5 This step verifies that the PCM is able to control the fuel injector If the test lamp flashes the PCM and the wiring are OK 6 This step tests if a ground is constantly being applied to the fuel injector DTC P0200 ee Schematic Reference Engine Controls Schematics Did you perform the Diagnostic System Check Engine Controls Go to Diagnostic System Check Go to Step2 Engine Controls 3 Monitor the Misfire Current counters with a scan tool Go to Step 4 Go to Step 3 Observe the Freeze Frame Failure Records data for this DTC Turn OFF the ignition for 30 seconds Start the engine Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame Failure Records data that you observed Does the DTC fail this ignition 1 Clear the DTCs with a scan tool 2 2 Idle the engine at the normal operating temperature Are any of the counters incrementing Go to Go to Step 4 Diagnostic Aids IMPCO Technologies Engine Service Manual 13 1C7 I nition System 4 3 liter Emission Certified GM Engine DTC P0200 cont d Turn OFF the ignition Remove the engine cover Refer to Engi
287. se the reguirements for service on certain compo nents Therefore the owner and servicing agent should review the operating condition of the eguipment and determine if more freguent inspections and maintenance cycles maybe required When performing maintenance on the engine shut off the engine and dis connect the battery negative cable to avoid injury or damage to the engine The engine installed in this eguipment may use one or both accessory drive belt configurations The drive belt may be incorporated to drive the water pump alternator and addition pumps or devices It is important to note the drive belt is an integral part of the cooling and charging system and should be inspected at a minimum according to the maintenance schedule in this section and in extremely hot and dirty envi ronments more often When inspecting the belts check for e Cracks e Chunking of the belt e Splits e Material hanging loose from the belt e Glazing hardening If any of these conditions exist the belt should be replaced with an OEM replacement belt 2 IMPCO Technologies Engine Service Manual V BELT SYSTEMS Check the belt tension by pressing down on the midway point of the longest stretch between two pulleys The belt should not depress beyond 13mm 1 2 inch If the depression is more than allowable adjust the tension Do not over tighten the tension of the belt Over tightening may cause overload on the bearings and pulleys of the dr
288. section Does DST display MAP voltage of 0 05 or less with the engine idling Key OFF 5 Disconnect the TMAP sensor from the wiring harness Jumper the 5 volt reference pin 3 and MAP signal circuit pin 4 together Key ON Does the DST display MAP voltage of 4 5 volts or greater connector and pins for corrosion Repair the to step 5 contamination or mechanical damage circuit as Any problems found necessary Refer to Wiring Repairs in Engine Electrical ey O o to Step 6 epair the Disconnect ECM connector circuit as Check for continuity between TMAP sensor connector signal pin 4 and ECM MAP signal Refer to 33 Wiring Repairs Do you have continuity between them tor continuity o to step 7 epair the connector 5 volt supply signal pin and ECM 5 circuit as volt supply pin 50 necessary Do you have continuity between them Refer to Wiring Repairs in Engine tor continuity to step 17 u connector ground pin 1 and ECM sensor ground circuit as pin 49 necessary Do you have continuity between them Refer to Wiring Repairs in Engine IMPCO Technologies Engine Service Manual 57 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine connector signal circuit p test light connected to battery voltage Disconnect ECM connector Check for continuity between TMAP sensor connector pin 3 and ECM 5 volt reference pin 50 Do you have continuity between them connector 5 vo
289. sensor connector 5 volt reference signal pin C and engine ground Do you have continuity Inspect TMAP AND ECM connectors pins for corrosion contamination or mechanical damage Any problems found Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete Disconnect ECM connector Check for continuity between TMAP sensor connector pin D and ECM pin 33 Do you have continuity between them Check for continuity between TMAP sensor connector pin D and engine ground Do you have continuity Inspect ECM connector and wire harness connector pins for corrosion contamination or mechanical damage Any problems found Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete Go to step 10 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to Step 11 as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical EN _ Ba Go to Step 16 Go to Step 14 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to step 15 as necessary Refer to Wiring Repairs in Engine Electrical Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical mE m mE Go to Step 16 Replace TMAP sensor Go to step 17 17 Is the
290. sensor connector signal pin B and ECM IAT signal pin 32 Do you have continuity between them Go to step 10 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Repair the Go to step 10 circuit as necessary Refer to Wiring Repairs in Engine Electrical e Check for continuity between TMAP sensor connector ground circuit pin Aand ECM sensor ground circuit pin 49 Do you have continuity between them Replace ECM Refer to ECM replacement in the Engine Controls Section Is the replacement complete Go to step 11 e Re check wire harness and TMAP sensor connectors for damage corrosion or contamination Were any problems found Repair the Go to Step 5 circuit as necessary Refer to Wiring Repairs in Engine Electrical 1 e Key OFF e Disconnect the ECM wire harness connector IMPCO Technologies Engine Service Manual 19 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine e Re check wire harness and TMAP sensor Repair the Go to Step 8 connectors for damage corrosion or contamination circuit as Were any problems found necessary Refer to Wiring Repairs in Engine Electrical Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operat
291. sensor wires may be mis routed and contacting the exhaust manifold Vacuum leaks can cause a lean exhaust condition especially at light load and idle conditions Exhaust leaks can cause a lean exhaust condition especially at light load and idle conditions A poor ECU ground to the engine block or battery negative Problems with the fuel system causing lean fuel mixtures such as low fuel pressure faulty mixture control solenoid or damaged fuel mixer assembly Never solder HO2S wires For the correct repair procedure refer to Wiring Repairs in the Engine Electrical Section 92 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 211 Closed Loop Multiplier High GOB Key On Engine Running DST Diagnostic Scan Tool connected in System Data Mode Run engine to full operating temperature and then idle for a minimum of 2 minutes Does DST display HO2S voltage fixed below 0 35 volts after 2 minutes of idle run time Disconnect ECM connector Disconnect HO2S wire harness connector Using a high impedance DVOM check for continuity between HO2S connector signal pin B and engine ground Do you have continuity Using a high impedance DVOM check for continuity between HO2S connector signal pin B and HO2S connector sensor ground pin A Do you have continuity between them Refer to Diagnostic aids for DTC 211 Did you check the diagnostic Aids for DTC 211 Replace
292. should not be disas sembled or rebuilt If the mixer fails to operate or develops a leak the mixer should be replaced with the OEM recom mended replacement parts When inspecting the mixer check for the following items e Check for any fuel leaks at the inlet fitting Check the fuel inlet hose for cracking splitting or chaff ing replace if any of these condition exist e Check to ensure the mixer is securely mounted e Check air inlet hose connection and insure clamp is tight check inlet hose for cracking splitting or chaffing re place if any of these condition exist IMPCO Technologies Engine Service Manual 7 OB Maintenance 4 3 liter Emission Certified GM Engine Check air cleaner element according to the Recommended Maintenance Schedule found in this sec tion Check fuel line to Throttle body mounted Fuel Trim Valve for cracking splitting or chaffing replace if any ofthese condition exist Check Throttle body return action to ensure throttle shaft is not sticking repair if necessary Check electrical connection to ensure connector is fully seated and locked Check for leaks at the throttle body and intake manifold Check Throttle cable for damage rubbing and kinking and free movement repair if necessary EXHAUST SYSTEM AND CATALYTIC CONVERTER INSPECTION AND MAINTENANCE IMPORTANT The exhaust system on this emission certified engine contains an Exhaust Gas Oxygen Sensor EGO which
293. stems The ECM must see a valid Crankshaft position signal while running If no signal is present for 800ms or longer this fault will set 76 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 142 Crank Sync Noise Value s ves no Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section Go to Step 3 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical e Key On Engine OFF 5 0 volts Go to Step 4 Repair the circuit e Disconnect the CKP Crankshaft position Sensor necessary connector C009 Refer to Wiring e Using A DVOM check for voltage at the sensor Repairs in Engine connector pin A and engine ground Electrical Do you have voltage Key OFF Go to Step 5 Repair the circuit Disconnect ECM connector 001 as necessary Refer to Wiring Repairs in Engine Electrical Go to Step 6 Repair the circuit as necessary Refer to Wiring Repairs in Engine Electrical Using aDVOM check for continuity between CKP connector pin B and ECM connector pin 12 Repair the circuit Go to Step 7 as necessary Do you have continuity between them Refer to Wiring Repairs in Engine Electrical Repair the circuit Go to step 8 as necessary Refer to Wiring Repairs in Engine Electrical Go to Step 10 e Check that the ECM ground terminals G1 and G2 are clean and tight Are th
294. stored when the set Turn OFF the ignition and wait 30 seconds Disconnect the PCM connector Use a DMM set to the 400 mv AC hertz scale in order to observe the freguency between the KS signal circuit and the KS low reference circuit while tapping on the block with a non metallic object Refer to Measuring Freguency in Wiring Systems Does the DMM display a fluctuating freguency while tapping on the block Go to Step 6 Go to Step 4 1 Disconnect the KS 2 Test for an open in the KS signal circuit and low reference circuit Refer to Testing for Continuity in Wiring Systems Did you find and correct the condition Go to Step 11 Go to Step 5 Inspect for a poor connection at the knock sensor harness connector Refer to Testing for Intermittent and Poor Connections in Wiring Systems Did you find and correct the condition Go to Step 11 Go to Step 9 Test for a short to ground and for a short to voltage in the KS signal circuit Refer to Testing for Short to Ground and Testing for a Short to Voltage in Wiring Systems Did you find and correct the condition Go to Step 11 Go to Step 7 Test for a short to ground and a short to voltage in the KS low reference circuit Refer to Testing for Short to Ground and Testing for a Short to Voltage in Wiring Systems Did you find and correct the condition Go to Step 11 Go to Step 8 Inspect for a poor connection at the harness connector of the PCM Refer to Testing for Intermittent and Poor Conn
295. sure and intake manifold referred to as vacuum pressure Pressure Regulator A device to control the pressure of fuel delivered to the fuel injector s Primary Circuit The low voltage or input side of the ignition coil Propane An odorless colorless gas C3H8 found in natural gas and petroleum PTV Pressure Trim Valve Reactivity Refers to the tendency of an HC in the presence of Nox and sunlight to cause a smog forming reaction The lighter the HC the lower reactivity tends to be Regulator An assembly used to reduce and control the pressure of a liquid or vapor Resistance The opposition to the flow of current in an electrical circuit Measured in ohms IMPCO Technologies Engine Service Manual 5 OA General Information 4 3 liter Emission Certified GM Engine Rest Pressure Fuel pressure maintained within the system after engine shutdown Rich Mixture An air to fuel ratio below the stoichiometric ratio too much fuel SAE Society of Automotive Engineers Secondary Circuit The high voltage output side of the ignition coil SEFI or SFI Sequential Electronic Fuel Injection or Sequential Fuel Injection Sensors Devices that provide the control module with engine information as needed to properly control engine function Spark Line The portion of an oscilloscope pattern that represents the time during which the air fuel mixture is being burned in the combustion chamber Splice An electrical term for the joining of two
296. t Did you find and correct the condition Go to Step 17 Go to Step 12 Perform the Fuel System Diagnosis Refer to Fuel System Go to Symptoms Diagnosis Engine Did you find and correct the condition Go to Step 17 Mechanical 4 3L Replace the spark plugs Refer to Spark Plug Replacement Did you complete the replacement Go to Step 17 Replace the spark plug wires Refer to Spark Plug Wire Replacement Did you complete the replacement Go to Step 17 Replace the distributor cap Refer to Distributor Overhaul Did you complete the replacement Go to Step 17 Inspect or test for the following conditions Inspect the vacuum hoses for splits kinks and the correct connections Inspect for vacuum leaks at the throttle body and at the intake manifold Inspect the PCM grounds for being clean tight and in the correct location Inspect for contaminated fuel Refer to Alcohol Contaminants in Fuel Diagnosis Without Special Tool or Alcohol Contaminants in Fuel Diagnosis With Special Tool Test for the correct fuel pressure Refer to Fuel System Diagnosis Inspect for poor connections at the ignition coil Inspect for faulty spark plug wires or coil wire Refer to Spark Plug Wire Inspection Inspect for fouled or damaged spark plugs Refer to Spark Plug Inspection Inspect the distributor cap and distributor for damage Refer to Distributor Inspection Test the ignition coil for the correct output with the 26792
297. t parameters of DTC 212 check for any stored codes Does the engine operate normally with no stored codes 96 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 97 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 221 Closed Loop Multiplier High Gasoline DK GRN ORN Sensor Ground Heater PNK DK GRN To Engine Ground To System Power Relay Conditions for Setting the DTC e Heated Oxygen Sensor Functional Fault Closed Loop multiplier out of range at limit of 35 MIL On during active fault Adaptive Enabled Closed Loop Enabled Circuit Description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the Adaptive multiplier This fault sets if the Closed Loop multiplier exceeds the limits of normal operation When the multiplier cannot correctly modify the fuel flow within its limits the limit is enforced Diagnostic Aids If any other DTCs are present diagnose those first Oxygen Sensor Wire Heated Oxygen sensor wires may be mis routed and contacting the exhaust manifold Vacuum Leaks Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at especially at light load Injectors System will be lean if an injector driver or driver circuit fails open T
298. tained to the engine or chassis e Check to insure any additional electrical devices installed by the owner are properly installed in the system e Check the MIL charging and oil pressure lights for operation by starting the engine and checking that the light illuminates for the prescribe period of time before turning out IMPCO Technologies Engine Service Manual 3 OB Maintenance 4 3 liter Emission Certified GM Engine ENGINE CRANKCASE OIL OIL RECOMMENDATION Prior to changing the oil select oil based on the prevailing daytime temperature in the area in which the equipment will be operated The chart in figure 1 is a guide to selecting the proper crankcase oil IMPORTANT Oils containing solid additives non detergent oils or low quality oils are not recommended by the engine manufacturer RECOMMENDED SAE VISCOSITY GRADE ENGINE OILS FOR THE BEST FUEL ECONOMY AND COLD STARTING SELECT THE LOWEST SAE VISCOSITY GRADE OIL FOR THE EXPECTED TEMPERATURE RANGE HOT WEATHER IF NEITHER SAE 10W 30 NOR SAE 15W 40 GRADE OILS ARE AVAILABLE SAE 30 GRADE MAY BE USED AT TEMPERATURES ABOVE 4 DEGREES 40 F SAE 40 GRADE MAY BE USED AT TEMPERATURES ABOVE 27 DEGREES 80 DO NOT USE SAE 10W 40 GRADE OIL OR ANY OTHER GRADE NOT RECOMMENDED SAE 15 40 SAE 10 30 PREFERRED COLD WEATHER Figure 1 Engine Oil Viscosity Recommendation USE OF SUPPLEMENTAL ADDITIVES Use of the oi
299. tch or engine control switch is released at the time the plunger return spring causes the pinion to disengage To prevent excessive overrunning release the ignition switch or engine control switch from the crank position as soon as the engine starts DIAGNOSIS Before removing any unit in a cranking circuit for repair the following checks should be made Battery Refer to the appropriate service manual to determine battery condition Wiring Inspect wiring for damage Inspect all connections to the starter motor solenoid ignition switch battery and all ground connections Clean and tighten all connections as required Starter Solenoid and Ignition Switch Inspect to determine their condition Starter Motor Noise To correct starter motor noise during starting use the following procedure 1 Refer to Starter Motor Noise Diagnosis Chart in this Section to determine the problem 2 When starter motor noise diagnosis indi cates that the pinion should be closer to the flywheel check to make sure the proper starter motor was installed When initial starter motor installation is performed shim s are not used 3 When starter motor noise diagnosis indi cates that the pinion should be moved away from the flywheel add 0 015 inch double shims until noise disappears do not exceed 0 045 inches Starter Motor If the battery wiring and switches are in satisfactory condition and the engine is known to be functioning
300. ted 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine 170 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Starter 1C5 GENERAL INFORMATION English and Metric Fasteners CAUTION Late model engines use a combination of English and Metric threaded fasteners The components effected are starter motor engine mounts and flywheel housing mounting Verify that the proper fasteners are used whenever removing or replac ing one of these components CRANKING CIRCUIT The cranking circuit consists of the battery starter motor and ignition switch STARTER MOTOR Two different starter motors are used on GM engines The SD300 is a straight drive starter with the pinion driven directly by the armature shaft Each starter has pole pieces arranged around the armature that are energized by wound field coils The PG260 achieves gear reduction at a ratio of 5 1 through planetary gears It s relatively small size and light weight offers improved cranking performance and reduced current reguirements Solenoid windings are energized when the igni tion switch is in the start position The resulting plunger and shift lever movement causes the pinion to engage the engine flywheel ring gear the solenoid main contacts to close and cranking takes place When the engine starts the pinion over running clutch protects the armature from exces sive speed until the ignition swi
301. tem Diagnostic Scan Tool DST Test Description The numbers below refer to step numbers on the diagnostic table 4 Connect fuel pressure gage as shown in illustration Wrap a shop towel around the fuel connection to absorb any small amount of fuel leakage that may occur when installing the gage With ignition ON and the fuel pump running pressure should be 284 325 kPa 41 47 psi This pressure is controlled by spring pressure within the regulator assembly 6 When the engine is idling manifold pressure is low High Vacuum and is applied to the pressure regulator diaphragm Vacuum will offset spring pressure and result in a lower pressure Fuel pressure at idle will vary somewhat depending on barometric pressure but should be less then the pressure noted in step 4 11 Fuel pressure that drops off during acceleration or cruise may cause a lean condition and result in a loss of power surging or misfire This condition can be diagnosed using the Diagnostic Tool If the fuel in the system is very lean the Heated Exhaust Gas Oxygen HEGO will stop toggling and output voltage will drop below 300 mV Also injector pulse will increase 14 Fuel pressure below 284 kPa 41 psi may cause lean condition and may set a DTC Driveablity conditions can include hard starting cold hesitation and lack of power or misfire 15 Restricting the fuel return pipe cause the fuel pressure to build above the regulated pressure With battery vo
302. terference This noise could be interpreted by the ECM as ignition pulses and the sensed RPM becomes higher than the actual speed The ECM then delivers too much fuel causing the system to go rich TMAP Sensor A higher manifold pressure than normal can cause the system to go rich Temporarily disconnecting the MAP Sensor will allow the ECM to set a default value for MAP IAT Sensor Check for a shifted sensor that could cause the ECM to sense lower than actual temperature of incoming air This can cause a rich exhaust condition ECT Sensor Check for a skewed sensor that could cause the ECM to sense engine temperature colder than it actually is This could also cause a rich exhaust condition 108 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 242 Adaptive Rich Fault Low Limit T JJ atom Vae e Perform the On Board OBD System Check Are any other DTCs present Visually and physically check the following items The air intake duct for being collapsed or restricted The air filter for being plugged The HO2S sensor installed securely and the wire leads not contacting the exhaust manifold or ignition wires ECM grounds for being clean and tight Refer to Section 1 Engine Electrical Power and Ground Distribution Fuel System Diagnostics Refer to Section 1B Fuel System Diagnostics Was a repair made Diagnose any other DTC codes before proceeding with this ch
303. the On Board OBD System Check Go to Step 2 Go to OBD System Check Section e Key ON Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Fault Mode Go to Intermittent Does DST display DTC 531 section Key OFF Go to Step 5 Go to Step 4 Disconnect ECM connector Using DVOM check for continuity between ECM 5 volt reference LT GRN R pin 50 and engine ground Do you have continuity Replace ECM Go to Step 7 Is the replacement complete Step 5 While monitoring DVOM for continuity between Go to Step 6 ECM 5 volt reference and engine ground disconnect each sensor below one at a time to find the shorted 5 volt reference When continuity to ground is lost the last sensor disconnected is the area of suspicion Inspect 5volt reference supply wire leads for shorts before replacing the sensor ECT CHT TMAP FPP 5 1 TPS2 Crankshaft Sensor Camshaft Sensor While disconnecting each sensor one at a time did you loose continuity e Replace Sensor Go to step 7 Is the replacement complete IMPCO Technologies Engine Service Manual 133 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle
304. the in line fuel filter for restrictions Ignition System Checks Check for the proper ignition output voltage using the spark tester J26792 or the equivalent that the spark plugs are correct use R42LTS Check the spark plugs Remove the plugs and inspect them for the following conditions Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Check the Crankshaft Position CKP sensor Additional Check Check the ECU grounds for being clean tight and in their proper locations Check the generator output voltage Check the vacuum hoses for kinks or leaks Check Transmission 28 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine System Diagnostics 1B4 Restricted Exhaust System Diagnosis Exhaust System Description The emission certified engine has been designed and calibrated to meet the emission standards in effect for 2004 To help meet the emission requirements the vehicle has been equipped with a Three Way Catalytic TWC muffler The catalyst muffler is a three way catalyst sound damping and spark arresting unit Besides controlling the noise created from the combustion process and preventing sparks from escaping from the exhaust system the most important function is treating the exhaust gases which are created from the combustion process The three way catalyst consists of ahoneycomb coated with a mixture of platinum palladium and rhodium The hot
305. the intake manifold in response to electrical from the control module Fuel Lock A solenoid controlled valve located in the fuel line to stop the flow when the engine stops or the ignition switch is off Gasohol 10 percent ethanol 90 percent gasoline Often referred to as E 10 Gasoline A motor vehicle fuel that is complex blend of hydrocarbons and additives Typical octane level is 89 Greenhouse Effect A scientific theory that suggests that excessive levels of carbon dioxide from the burning of fossil fuels is causing the atmosphere to trap heat and cause global warming HD 10 A fuel of not less than 80 liquid volume propane and not more than 10 liquid volume propylene HD 5 A fuel of not less than 90 liquid volume propane and not more than 5 liquid volume propylene HDV Heavy Duty Vehicle Hg Chemical symbol for mercury Used in reference to vacuum in of Hg Hydrocarbon A chemical compound made up of hydrogen and carbon HC A major pollution emission of the internal combus tion engine Gasoline and almost all other fuels are hydrocarbons Hydrostatic Relief Valve A pressure relief device installed in the liquid propane hose on a propane fuel system IAT Intake Air Temperature Ideal Mixture The air fuel ratio at which the best compromise of engine performance to exhaust emissions is obtained Typically 14 7 1 Ignition Reserve The difference between available voltage and the required voltage ILEV Inherently L
306. the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until the code is cleared This fault should be erased after diagnosis by removing battery power It will not self erase During this active fault Power Derate level 2 will be enforced When this is enforced maximum throttle position will be 20 This is enforced until the fault is manually cleared 126 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 514 RTI 1 Loss vag Ye No 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code section Does DTC 514 reset with the engine idling 3 e Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical e Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehic
307. the test the lamp will stay illuminated and the DTC is current ACTIVE All DTC s are stored as historical faults until they are cleared All DTC s except the ECM related DTC s will automatically clear from memory if the DTC does not reset within 50 consecutive engine run cycles While a Diagnostic Trouble Code is current for a sensor the ECM may assign a default limp home value and use that value in its control algorithms All of the system diagnostic self tests run continuously during normal vehicle operation The Diagnostic Trouble Codes can be read by using either the MIL lamp or a laptop computer Refer to Using a Laptop Computer to Diagnose the Spectrum System and Using a Diagnostic Jumper to Diagnose the ECI System located in this section Diagnostic Trouble Codes can be cleared from memory with a laptop computer or by turning the ignition key to the OFF position and removing the system main power fuse F3 for 15 seconds If more than one DTC is detected always begin with the lowest number DTC and diagnose each problem to correction unless directed to do otherwise by the fault tree The DTC s are numbered in order of importance Having DTC 112 and DTC 122 both concerning the oxygen sensor is possible By repairing DTC 112 first the problem causing the DTC 122 may also be corrected IMPCO Technologies Engine Service Manual 3 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine USING A LAPTOP COMPUTER TO DI
308. the time the diagnostic fails The first time the diagnostic fails the control module 5 This step checks the crankshaft position sensor DTC P0335 Sep Con ene Jes N Schematic Reference Engine Controls Schematics Did you perform the Diagnostic System Check Engine Go to Diagnostic Controls System Check Go to Step2 Engine Controls Does the vehicle start and continue to run Go to Intermittent Conditions Go to Step 3 Disconnect the crankshaft position CKP sensor Turn ON the ignition leaving the engine OFF Probe the CKP sensor harness connector 12 volt reference circuit with a test lamp connected to a ground Does the test lamp illuminate Go to Step 4 Go to Step 6 Connect a test lamp between the 12 volt reference circuit in the CKP sensor harness connector and the sensor low reference circuit Does the test lamp illuminated Go to Step 5 Go to Step 7 IMPCO Technologies Engine Service Manual 25 1C7 Ignition System 4 3 liter Emission Certified GM Engine 26 DTC P0335 cont d Value s es No 1 Turn OFF the ignition 2 Install the gray jumpers from the 35616 Connector Test Kit between the engine harness connector and the sensor connector of the 12 volt reference circuit and low reference circuit Connect a DMM set to the duty cycle position 40 60 between the sensor signal circuit and a ground circuit Select AC voltage and press the Hz button twice in order to display the du
309. tically and may set false DTCs Important Do not reuse the original O ring 1 Replace the CKP sensor O ring 2 Lubricate the O ring with clean engine oil before installing the CKP sensor Important Make sure the CKP sensor mounting surface is clean and free of burrs 3 Install the CKP sensor Notice Refer to Fastener Notice in Cautions and Notices 4 Install the sensor mounting bolt Tighten Tighten the CKP sensor mounting bolt to 9 N m 80 Ib in 5 Connect the CKP sensor harness connector 4 3 liter Emission Certified GM Engine Camshaft Position CMP Sensor Replacement Removal Procedure 1 Disconnect the spark plug wires and ignition coil wire from the distributor Refer to SparkPlug Wire Replacement 2 Disconnect the camshaft position CMP sensor harness connector from the distributor 3 Remove the distributor cap screws IMPCO Technologies Engine Service Manual 302854 302829 157984 29 157986 5 Remove the rotor screws 4354 6 Remove the rotor 156748 30 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Ignition System 1C7 7 Align the square slot in the reluctor wheel with the CMP sensor 156754 8 Remove the CMP screws 4341 9 Remove the CMP sensor 301398 IMPCO Technologies Engine Service Manual 31 1C7 Ignition System 4 3 liter Emission Certified GM Engine Installation Procedure
310. tics Remove the air filter and check for dirt or restriction Check the vehicle transmission Refer to the OEM transmission diagnostics Check for a restricted fuel filter contaminated fuel or improper fuel pressure Refer to LPG Fuel System Diagnosis Check for the proper ignition output voltage with the spark tester J 26792 or the equivalent Check for proper installation of the mixer module assembly Check all air inlet ducts for condition and proper installation Check for fuel leaks between the LPR and the mixer Verify that the LPG tank manual shut off valve is fully open Verify that liguid fuel not vapor is being delivered to the LPR Check the Heated Exhaust Gas Oxygen Sensor HEGO for contamination and performance Check for proper operation of the MAP sensor Check for proper operation of the TPS and FPP sensors Check the exhaust system for a possible restriction Inspect the exhaust system for damaged or collapsed pipes Inspect the muffler for signs of heat distress or for possible internal failure Check for possible plugged catalytic converter Check the engine for the following Engine compression Valve timing Improper or worn camshaft Refer to Engine Mechanical in the Service Manual Check the ECM grounds for being clean tight and in their proper locations Check the generator output voltage If all procedures have been completed and no malfunction has been found review and inspect the fo
311. til fault is cleared Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 enforced Circuit Description Random Access Memory is located within the microprocessor that can be read from or written to at any time The System Fault Codes and the Adaptive Learn Table are among the data stored in RAM This fault will set if the ECM detects a problem accessing or writing information to RAM This fault will not self erase and must be cleared manually 130 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 516 Ram Failure Value s Ye 1 Did you perform the On Board OBD System Check Go to Step 2 Go to OBD System Check Section 2 Key On Engine Running Go to Step 3 Intermittent DST Diagnostic Scan Tool connected in problem System Data Mode Go to Intermittent Clear system fault code section Does DTC 516 reset with the engine idling 3 e Check all ECM power and ground circuits Refer Go to Step 4 Repair the circuit to power and ground distribution in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical e Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the
312. tion OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 134 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 67 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 135 BP Low Pressure Bosch TMAP TMAP SENSOR Conditions for Setting the DTC Barometric Pressure Check Condition Key On Fault Condition BP less than 8 3 psia MIL On for active fault and for 2 seconds after active fault Adaptive Disabled for remainder of key on cycle Closed Loop Enabled Circuit Description The BP Barometric Pressure is estimated from the TMAP sensor The barometric pressure value is used for fuel and airflow calculations This fault sets in the event the BP value is out of the normal range 68 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 135 BP Low Pressure Bosch TMAP a Re D System Check Section Intermittent problem Go to Intermittent section Key _ o to Step 4 o to step 8 Disconnect the TMAP sensor from the wiring harness Jumper the 5 volt reference pin 3 and MAP signal pin 4 together Key ON gt o to ste
313. tion from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 145 check for any stored codes Does the engine operate normally with no stored codes 90 IMPCO Technologies Engine Service Manual IMPCO Technologies Engine Service Manual 91 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 211 Closed Loop Multiplier High LPG B BK LG Sensor Ground BK Heater To System Power Relay To Engine Ground Conditions for Setting the DTC Heated Oxygen Sensor Check Condition Engine running Fault Condition Closed Loop multiplier out of range greater than 3596 MIL Disabled Adaptive Enabled but not updated when Closed Loop is at limit Closed Loop Enabled Circuit description The HO2S sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Closed Loop multiplier and the adaptive multiplier This fault sets if the Closed Loop multiplier exceeds the limits of normal operation and cannot correctly modify the fuel flow within its limits Diagnostic Aids Always diagnose any ECM codes that are present before beginning this diagnostic procedure e Heated Oxygen
314. tion in engine as necessary electrical section Refer to Wiring Are the power and ground circuits Ok Repairs in Engine Electrical Replace ECM Go to Step 4 Is the replacement complete Remove all test equipment except the DST System OK Go to OBD Connect any disconnected components fuses etc System Check Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 555 check for any stored codes Does the engine operate normally with no stored codes IMPCO Technologies Engine Service Manual 139 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 556 RTI 3 Loss ECM Microprocessor Conditions for Setting the DTC Engine Control Module Check Condition Key on Fault Condition Internal microprocessor error MIL On until code is cleared by technician Adaptive Disabled for the remainder of the key on cycle Closed Loop Enabled Power Derate level 2 until fault is cleared manually Circuit Description The ECM runs checks that must be satisfied each time an instruction is executed Several different things can happen within the microprocessor that will cause this fault The ECM will reset itself in the event this fault is set and the MIL will be on until th
315. ty cycle 4 Crank the engine Is the duty cycle within the specified range Go to Step 8 Go to Step 9 Repair the open or high resistance in the 12 volt reference Go to Step 15 circuit Refer to Wiring Repairs in Wiring Systems Go to Step 15 Go to Step 13 Did you complete the repair Go to Step 15 Go to Step 11 Go to Step 10 Go to Step 12 1 Repair the open or high resistance in the low reference circuit 2 Repair the circuit as necessary Refer to Wiring Repairs in Wiring Systems Did you find and correct the condition 1 Repair the open high resistance and for a short in the sensor signal circuit 2 Repair the circuit as necessary Refer to Wiring Repairs in Wiring Systems Did you find and correct the condition Check the CKP sensor and the crankshaft reluctor wheel for damage Refer to Crankshaft Position CKP Sensor Replacement or Crankshaft Position CKP Reluctor Ring Replacement Did you find and correct the condition 1 Check for a faulty connection at the CKP sensor 2 Repair the connector as necessary Refer to Connector Repairs in Wiring Systems Did you find and correct the condition Go to Step 15 Go to Step 13 Go to Step 15 za Go to Step 15 Go to Step 15 NN Go to Step 16 Important Inspect the CKP sensor mounting surface in order to verify that the surface is clean and free of debris Replace the CKP sensor Refer to Crankshaft Position CKP Sensor Replacement Did you find and corr
316. ult is set the Adaptive Learn will be disabled for the remainder of the key on cycle and the MIL will be on The engine will operate on a default MAP during this active fault Diagnostic Aids If the engine is running rough unstable or missing due to a suspected mechanical problem vacuum leak or other issue causing misfire these problems must be taken care before using the MAP diagnostic chart Failure to follow this recommendation will result in a false MAP diagnostic and repair procedure 52 IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic Trouble Codes 1C4 DTC 131 MAP HIGH PRESSURE Motorola TMAP Key On Engine running DST Diagnostic Scan Tool connected in System Data Mode Does DST display MAP pressure of 13 0 psia or greater with the engine idling e Key OFF e Disconnect TMAP sensor connector e Key ON Does the DST display MAP pressure less than 0 05 psia e Probe TMAP sensor ground circuit pin A with a test light connected to battery voltage Does the test light come on e Check TMAP mechanical connection for correct mounting or possible damage causing leakage Is the TMAP sensor mechanical connection Ok e Key OFF e Disconnect ECM connector and inspect terminals for damage corrosion or contamination Is the connection Ok Replace TMAP sensor Is the repair complete e Disconnect ECM connector and check for continuity between TMAP connector sensor groun
317. umbers below refer to the step numbers on the diagnostic table 2 This step ensures that the malfunction is present 3 This step ensures that the KS is capable of detecting detonation and producing a signal 6 If the KS signal wire is shorted to ground or shorted to voltage the KS may still produce a signal 7 If the KS low reference is shorted to ground shorted to voltage the KS may still produce a signal DTC P0327 sel am _ ___ __ Schematic Reference Engine Controls Schematics Go to Diagnostic System Check Did you perform the Diagnostic System Check Engine Controls 1 Go to Step2 Engine Controls 2002 Van August 7 2001 IMPCO Technologies Engine Service Manual 23 1C7 Ignition System 4 3 liter Emission Certified GM Engine DTC P0327 cont d Important an engine knock can be heard repair the engine mechanical condition before proceeding with this diagnostic 1 Use a scan tool in order to observe the Freeze Frame Failure Records data for this DTC 2 Turn OFF the ignition for 30 seconds 3 Start the engine 4 Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as closely as possible to the Freeze Frame Failure Records conditions Go to Intermittent Does the DTC fail this ignition Go to Step 3 Conditions Turn ON the ignition with the engine OFF Use a scan tool in order to save the Freeze Frame Failure Records data
318. und in many crude oils Backfire Combustion of the air fuel mixture in the intake or exhaust manifolds A backfire can occur if the intake or exhaust valves are open when there is a mis timed ignition spark Benzene An aromatic C6H6 Sometimes blended with gasoline to improve antiknock value Benzene is toxic and suspected of causing cancer Bi Fueled A vehicle equipped to run on two fuels at the same time such as a fumigated diesel Blow By Gases formed by the combustion of fuel and air which ordinarily should exert pressure only against the piston crown and first compression ring When rings do not seal these gases blowby escape down the side of the piston into the crank case BTU British Thermal Unit A measurement of the amount of heat required to raise the temperature of 116 of water 1 degree F Butane An odorless colorless gas 4 10 found in natural gas and petroleum One of the five LP gases CAFE Corporate Average Fuel Economy CARB California Air Resources Board Carbon Monoxide CO A chemical compound of a highly toxic gas that is both odorless and colorless Carburetor An apparatus for supplying an internal combustion engine a mixture of vaporized fuel and air Cathode Ray Tube A vacuum tube in which cathode rays usually in the form of a slender beam are projected on a fluorescent screen and produce a luminous spot Circuit A path of conductors through which electricity flows before it returns to its sourc
319. unted Malfunction Indicator Lamp MIL for indication of system problems MALFUNCTION INDICATOR LAMP MIL Most engine control system related problems that affect emissions or driveability of the vehicle will set a DTC Diagnostic Trouble Code and illuminate the Malfunction Indicator Lamp The MIL has the following functions 1 It notifies the driver of a problem with the fuel system ignition system or emission control system so the driver can arrange for service as soon as possible 2 It will display DTC s that have been stored due to a system malfunction The lamp should come on when the key is in the ON position and the engine is not running This feature verifies that the lamp is in proper working order Ifthe lamp does not come on with the vehicle key on engine off repair it as soon as possible Once the engine is in start or run mode the lamp should go off If the lamp illuminates while the engine is in the start or run mode there is a current Diagnostic Trouble Code Spectrum Diagnostic Trouble Codes DTC Diagnostic Trouble Codes are set when the Spectrum ECM Electronic Control Module runs a diagnostic self test and the test fails When DTC is set the ECM will illuminate the Malfunction Indicator Lamp on the instrument panel and save the code in memory The ECM will continue to run the self test unless the DTC is an oxygen sensor lean oxygen sensor rich or an internal ECM related DTC If the system continues to fail
320. ure Check Condition RPM greater than 800 Throttle Command less than 10 steady MAP and TPS Fault Condition MAP greater than 18 psia TPS less than 10 and engine RPM greater than 1800 MIL On for remainder of key on cycle Adaptive Disabled for remainder of key on cycle Closed Loop Enabled and allowed to stay at limit Misc Fueling is based on RPM and TPS Limp Home Condition during this fault Circuit Description The TMAP is a combined inlet manifold temperature and pressure sensor connected to the intake manifold It is used to measure the pressure of air in the manifold prior to induction into the engine The pressure reading is used in conjunction with other inputs to determine the airflow rate to the engine which also determines the fuel flow rate This fault will set when the MAP reading is higher than it should be for the given TPS and RPM When the fault is set the Adaptive Learn will be disabled for the remainder ofthe key on cycle and the MIL will be on The engine will operate on a default MAP during this active fault Diagnostic Aids If the engine is running rough unstable or missing due to a suspected mechanical problem vacuum leak or other issue causing misfire these problems must be taken care before using the MAP diagnostic chart Failure to follow this recommendation will result in a false MAP diagnostic and repair procedure IMPCO Technologies Engine Service Manual 4 3 liter Emission Certified GM Engine Diagnostic
321. use a DTC to be set by the ECU 2 With the engine idling observe the pressure reading on the secondary test port Goto Fuel Control System 2 Is the fuel pressure WITHIN the specified range Diagnosis Go to Step 7 Inspect the air intake stream between the mixer assembly and the throttle body for leaks Inspect the fuel hose connection between the LPR and mixer assembly for damage or leak age Inspect the vacuum hoses to the FTV solenoid Was a problem found and corrected Go to Step 26 Go to Step 22 B Go to Step 12 Go to Step 9 IMPCO Technologies Engine Service Manual 3 Connect a water column gauge or a manom eter to the secondary test port of the low pres sure regulator LPR Crank the engine and observe the pressure reading for the LPR secondary pressure Does the fuel pressure indicate a vacuum is pres ent 1B1 LPG Fuel System Diagnostics 4 3 liter Emission Certified GM Engine 1 Remove Air induction hose to the mixer 2 Observe the air valve for movement while the engine is cranking Note Movement of the air will be minimal at cranking speeds Does the air valve move when the engine is Go to Step 11 Go to Step 10 cranked 1 Inspect the air intake stream to the mixer assembly and the throttle body for vacuum leaks 2 Inspect the vacuum hoses from the mixer to the PTV solenoids for proper connection and condition Was a problem found and repaired Go to Step 26 Goto Step 24 Inspect the fu
322. uses a numerical display in place of a gauge and is usually of the high imped ance type DTC Diagnostic Trouble Code DST Diagnostic Scan Tool DVOM Digital volt ohmmeter ECT Engine Coolant Temperature ECM Electronic Control module IMPCO Technologies Engine Service Manual 3 OA General Information 4 3 liter Emission Certified GM Engine EFI Electronic Fuel Injection A fuel injection system which uses a microcomputer to determine and control the amount of fuel required by and injected into a particular engine EGR Exhaust gas recirculation EPA Environmental Protection Agency A regulating agency ofthe Federal government which among other duties establishes and enforces automotive emissions standards Ethanol Grain alcohol C2H5OH generally produced by fermenting starch or sugar crops Evaporative Emissions Controls An automotive emission control system designed to reduce hydrocarbon emissions by trapping evaporated fuel vapors from the fuel system Excess Flow Valve A check valve that is caused to close by the fuel when the flow exceeds a predetermined rate FTV Fuel Trim Valve FFV Flexible Fuel Vehicle Firing Line The portion of an oscilloscope pattern that represents the total amount of voltage being expended through the sec ondary circuit FMVSS Federal Motor Vehicle Safety Standards FPP Foot Pedal Position Sensor Fuel Injector a spring loaded electromagnetic valve which delivers fuel into
323. ve the correct controller 5 Plug connector into controller 4 3 liter Emission Certified GM Engine 6 Push lock into place 7 Mount controller into mounting bracket 8 Reconnect the battery cable 9 Install Diagnostic service tool 10 Start engine 11 Check for any DTC codes and clear 12 Verify engine is in closed loop and no MIL lights are present HEATED EXHAUST GAS OXYGEN SENSOR REPLACEMENT 1 Disconnect Negative battery cable 2 Disconnect the O 2 sensor electrical connector 3 Using a O 2 Sensor socket remove the O 2 Sensor and discard Installation Procedure IMPORTANT Before install the O 2 sensor lubricate threads with anti seize compound GM P N 5613695 or equivalent Avoid getting compound on the sensor tip 4 Install O 2 sensor Tighten 41 Nem 30 lb ft 5 Start engine 6 Check for any DTC codes and clear Verify engine is in closed loop and no MIL lights are present THREE WAY CATALYTIC CONVERTER MUFFLER REPLACEMENT 1 Remove the TWC muffler using the OEM end product processes Installation Procedure IMPORTANT The Three Way Catalytic converter is specifically de signed to meet the emission control of the certified en gine Use only the OEM specified parts 2 Install the TWC muffler using the OEM end product Fuel System 1E1 processes 3 Start engine 4 Check for any DTC codes and clear 5 Verify engine is in closed loop and no MIL lights are present REPAIR INSTRUCTIONS
324. vice Manual 17 1C7 Ignition System 4 3 liter Emission Certified GM Engine Go to Diagnostic System Check Go to Step2 Engine Controls Go to Diagnostic Trouble Code DTC List Go to Step 3 Go to Go to Step 5 Diagnostic Aids Did you perform the Diagnostic o Check Engine Controls 1 Turn ON the ignition with the engine OFF 2 Observe the DTC information with a scan tool Are there any other DTCs set Start the engine 2 Clear the DTCs with a scan tool 3 Allow the engine to reach operating temperature 4 Observe the Misfire Current Counters with a scan tool Are any of the Misfire Current Counters incrementing Observe the Freeze Frame Failure Records data for this DTC Turn OFF the ignition for 30 seconds Start the engine Operate the vehicle within the conditions for running the DTC You may also operate the vehicle within the conditions that you observed from the Freeze Frame Failure Records data Does the DTC fail this ignition cycle Go to Symptoms Engine Go to Step 6 ETI 4 3L Turn Ho ee one Com _ the ignition Disconnect the spark plug wire from the spark plug Refer to Spark Plug Wire Replacement Connect the J 26792 Spark Tester to the spark plug wire and a good ground Start and idle the engine Does the spark tester spark and is the spark consistent Go to Step 9 Go to Step 8 1 Turn OFF the ignition 2 Remove the spark plug wire fr
325. way radios electric motors etc The ignition secondary voltage shorted to a ground The Malfunction Indicator Lamp MIL circuit or the Diagnostic Test Terminal intermittently shorted to ground The Control Module grounds To check for the loss of the DTC Memory 1 Disconnect the TMAP sensor 2 Idle the engine until the Malfunction Indicator Lamp illuminates The ECU should store DTC The TMAP DTC should remain in the memory when the ignition is turned OFF Ifthe TMAP DTC does not store and remain the ECM is faulty IMPCO Technologies Engine Service Manual 1B4 System Diagnostics 4 3 liter Emission Certified GM Engine No Start DEFINITION The engine cranks OK but does not start Preliminary Checks e Refer to Important Preliminary Checks Control Module Checks e scan tool is available e Check for proper communication with both the ECM Check the 3A inline fuse in the ECM battery power circuit Refer to Engine Controls Schematics Check battery power ignition power and ground circuits to the ECM Refer to Engine Control Schematics Verify voltage and or continuity for each circuit Sensor Checks Check the TMAP sensor Check the Crankshaft Position CKP sensor Fuel System Checks Check for fuel pump electrical circuit Verify proper fuel pump pressure Verify proper Fuel rail pressure Refer to the Gasoline Fuel System Diagnosis Check Electrical connections at the injectors Ignition System Check
326. y IMPCO Technologies Engine Service Manual 16 4 3 liter Emission Certified GM Engine Remove o ring gasket and discard Installation Procedure IMPORTANT Lightly Lubricate the both the o rings of the throttle control device to adapter Cover Throttle body adapter opening to prevent de bris from entering engine until reassembly 1 Install o ring to the top of the throttle body assembly 2 Insert throttle body onto the bottom of the mixer 3 Tighten the four screws to specification Tighten 9 Nem 80 Ib in 4 Install Throttle adapter o ring 5 Install the Throttle body onto the manifold adapter line up the throttle cable bracket and install the four 4 re taining screw 6 Tighten the four screws to specification Tighten 12 Nem 106 Ib in 7 Connect the fuel vapor hose and secure clamp 8 Connect the balance line to the LPR 9 Connect the vacuum line 10 Connect both TPS electrical connectors 11 Connect the governor electrical connector 12 Connect the FTV electrical connector 13 Connect the throttle cable 14 Connect the air inlet duct 15 Start engine 16 Install the diagnostic tool and check for DTC codes and no MIL light MIXER REPLACEMENT Figure 3 Removal Procedure 1 Disconnect the negative battery cable 2 Remove the air intake duct 3 Remove the throttle body assembly Refer to Throttle Body Assembly Replacement 4 Remove the four 4 screws to the throttle body assem 4 3 liter Emission Certified G
327. y disconnected components fuses etc Using the DST clear DTC information from the ECM Turn the ignition OFF and wait 30 seconds Start the engine and operate the vehicle to full operating temperature Observe the MIL Observe engine performance and driveability After operating the engine within the test parameters of DTC 221 check for any stored codes Does the engine operate normally with no stored codes Go to Step 6 Go to Step 7 IMPCO Technologies Engine Service Manual 99 4 e Using a high impedance DVOM Check for Repair the Go to Step 5 continuity between HO2S connector signal pin B circuit as and HO2S sensor ground pin A reguired Do you have continuity Refer to Wiring Repairs in Engine Electrical IE 1C4 Diagnostic Trouble Codes 4 3 liter Emission Certified GM Engine DTC 222 Closed Loop Multiplier Low Gasoline DK GRN ORN Sensor Ground Heater PNK DK GRN ToEngine Ground To System Power Relay Conditions for Setting the DTC Heated Oxygen Sensor Functional Fault Closed Loop multiplier out of range at limit of 35 MIL On during active fault and for one update after active fault Adaptive Enabled Closed Loop Enabled Circuit Description The HO2S Heated Oxygen Sensor sensor is used to determine if the fuel flow to the engine is correct by measuring the oxygen content in the exhaust gas The ECM uses this information to correct the fuel flow with the Clos

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