DEALER SERVICE MANUAL UPDATE BULLETIN SUPPLEMENT
Contents
1. SUBTRACT SECOND READING FROM THE FIRST VOLTAGE VALUE SHOULD BE GREATER THAN 1 5 VOLTS 1517 5 NO TROUBLE FOUND CHECK SENSOR VACUUM SOURCE a CHECK SENSOR CONNECTION FORLEAKAGE OR RESTRICTION BE SURE THIS SOURCE IF OK REPLACE SENSOR SUPPLIES VACUUM SENSOR ONLY HOT STAMPED NUMBER KEYED INSERT 11 21 89 12 14 89 LS 8963 6E LS 9045 6E Figure 1 Color Key insert Figure 2 Hot Stamped Number CLEAR CODES AND CONFIRM CLOSED LOOP OPERATION AND NO SERVICE ENGINE SOON LIGHT Jia 90 199 5E DRIVEABILITY AND EMISSIONS REFER TO SERVICE MANUAL FOR CORRECT MAP SENSOR MAP SENSOR CIRCUIT WIRING DIAGRAM A B C TO SENSOR S MANIFOLD ABSOLUTE PRESSURE VACUUM TO SENSOR S 5 VOLT REFERENCE MAP SIGNAL SENSOR 1 GROUND 11 13 89 5 8906 6 33 MANIFOLD ABSOLUTE PRESSURE MAP OUTPUT CHECK SIGNAL VOLTAGE HIGH Circuit Description LOW VACUUM The Manifold Absolute Pressure MAP sensor responds to changes in manifold pressure vacuum The ECM receives this information as a signal voltage that will vary from about 1 to 1 5 volts at closed throttle idle to 4 5 4 8 volts at wide open throttle low vacuum If the MAP sensor fails the ECM will substitute a fixed MAP value and use the Throttle Position Sensor TPS to control fuel delivery Test Description Numbers below refer to circled A Code 33 will result if CKT 469 is2. SAM SHM BAM FZM HBM HHM F8M HOM 08M HJM YOM MSM BPM 188M 1 2 ACCUMULATOR 34 ACCUMULATOR SPRING COLOR SPRING COLOR ORANGE LT GREEN WHITE DR PLAIN ORANGE 17 GREEN WHITE DR PLAIN GREEN ORANGE LT GREEN RED WHITE OR PLAIN YELLOW YELLOW YELLOW REO U BLUE YELLOW VIDLET YELLOW 0 Ju RANGE LT GREEN ORANGE IT GREEN WHITE GR PLAIN WHITE OR PLAIN ET ORANGE LT GREEN ORANGE LT GREEN WHITE QR PLAIN YELLOW ORANGE LT GREEN WHITE PLAIN H0188 4L80 R 1 Figure 1 ERU e CHEVROLET MOTOR DIVISION Service CHEVROLET sa Motors Corporation September 1 989 Service Ospariment SERVICE 1 Update c Bulletin 916521R Corporsta Bulletin No Subject PACKARD 32 WAY CONNECTOR IDENTIFICATION and Year 1980 90 G J L W Y CARS AND ALL TRUCKS WITH GMP4 ECM APPLICATIONS TO ALLCHEVROLET DEALERS This bulletin serves to clarify the labeling of the Packard 32 way connectors used on the GMP4 under dash ECMs Currently a common strain relief is used in both the C D 32 pin and the E F 32 pin connectors To properly identify these connectors the strain reliefs must be removed Use the lettering on the connector as shown on the attached document The colors used at this time for the 32 pin E F connector are yellow mint green or orange This updates any previous information released concerning identificati
3. 12 9 LAM LBM LCM LOM LFM 741845 14270 580662 8496 10851372 157 199 MSM 793 1023 115 148 13111773 190257 SHM TLM 742 847 108 123 1593 2023 231 293 MANUAL 2ND BAM BPM FBM FTM FUM FZM HJM 1127 1286 163 188 1127 1286 163 186 MANUAL LO MEM MJM NNM SAM SHM TLM TNM WAM WBM WCM YOM DBM HHM MSM 175 226 1205 1554 175228 1000 RPM LAM LBM LCM LOM LFM 173 197 1191 1359 173197 Line pressure is basically controlled by pump output and the pressure regulator valve In addition line pressure 15 boosted in Reverse Second and Lo by the reverse boost valve Also in the Neutral Drive Intermediate and Reverse positions of the selector lever the line pressure should increase with throttle opening because of the T V system The pressure is controlled by the T V cable the throttle lever and bracket assembly and the T V link as well as the contro valve assembly The main line pressure tap plug is located on the left side of the transmission above the outside manual lever LHOOC3 41 50 2 Figure 2 90 77 7A Chevrolet Dealer CHEVROLET MOTOR DIVISION H Section Generat Motors Corporation CHEVROLET Service November 1989 Service Department Update Bulletin oe _ Corporate Bulletin No sujet REVISED ACCUMULATOR SPRING CHART Model and Year
4. Number CHEVROLET MOTOR DIVISION Gee 2 Ms 5 es n ate July 1 990 Bulletin EO 065008 Carporate Bulletin No sujet BRAKES Model and Year 1988 90 AND 1989 90 S T M AND 1990 R V AND G TRUCKS TO ALL CHEVROLET DEALERS The attached chart see Figure 1 is a revised code 5 diagnostic chart The revised chart requires a check of wiring and the transfer case switch operation before the control valve is replaced on 4 wheel drive vehicles The chart also revises code 5 diagnostic information in the following service manuals 1988 C K 1989 C K 1990 C K 1990 AND G 1989 S T 1990 S T 1989 M VAN 1990 M VAN Uu m lt LL C gt m COPYHIGHT 1990 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED Chevrolet bulletins are intended for use by professional technicians NOT a do it yoursalfer They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely If a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD148J Rev 12 89 5 EXCESSIVE
5. Section 6E1 6E2 and 6E3 This information applies to all MAP Sensors on 1980 1990 vehicles with gasoline engines except turbocharged with green standard MAP sensor electrical connector insert or the solid black MAP sensor electrical connector insert The revised chart and facing page information is as follows Diagnostic Chart C 1D and facing page The updated chart and facing page information is as follows Diagnostic Chart Code 33 and facing page Diagnostic Chart Code 34 and facing page Diagnostic Chart Code 63 and facing page Diagnostic Chart Code 64 and facing page 7 2 LL C U O gt a LL COPYRIGHT 1990 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED LLL _ Chevrolet bulletins are intended for use by professional technicians NOT a doa it yoursaifar They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely If a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD148J Rev 12 99 DRIVEABILITY EMISSIONS RE
6. 1990 B Y CARS AND K G L M S T V TRUCKS WITH 4L60 700R4 AUTOMATIC TRANSMISSION TO ALL CHEVROLET DEALERS This bulletin covers revised 1 2 and 3 4 Accumulator Spring Chart The new chart is applicable to all 1990 THM 700 R4 HYDRA MATIC 4L60 transmissions See Figure 1 Use the following chart to update your 1990 HYDRA MATIC 4160 Unit Repair Service Manual Section page 4L60 50 Figure 110 u gt m U O gt ITI COPYRIGHT 1989 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED 333 N Chevrolet bulletins are intended for use by protessional technicians NOT do it yourselfer They are written to inform these technicians of conditions that may occur on sorne vehicles or to provide information that could assist in tne proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD 1480 Rev 8 86 90 89 7 1990 MODELS CHM CJM KCM RAM WOM CAM MNM WAM CCM KOM LAM LBM LCM LOM WBM FUM
7. 5 0 10 K 0 10 30 A 000 15 A 130 0 50 0 75 TO COLUMN 0 15 50 5 80 0 80 1 DO 0 00 20 20 0 20 50 0 20 20 009 e 15 RECOMMENDED 0 90 0 75 150 O 08 31 0 50 75 0 30 900 15 0 25 75 RECOMMENDED 0 31 1 00 2 25 050 100 0 00 75 0 43 43 0 00 15 RECOMMENDED NOTE NOT ADJUSTABLE Vica Whee Systems General Motors Proving Ground Michigan 48042 2001 November 17 1989 1990 GENERAL MOTORS TRUCK WHEEL ALIGNMENT SPECIFICATIONS DEGREES TRUCK LINE CAMBER CROSS CASTER CROSS TOTAL TOE STEERING WHEEL ANGLE G 10 20 50 4 75 1 00 1 00 25 3 75 A 20 30 25 75 lt H _ V ALL 150 75 1 00 8 00 100 1 00 0 2 23 50 NOTES ACTUAL CORRECTED CASTER ANGLE x ALIGNER ANGLE FRAME RAIL ANGI FRAME ANGLE 5 NEGATIVE WHEN LOWER IN REAR AND POSITIVE WHEN LOWE R IN FRONT V VEHICLE CASTER AND CAMBER ARE NOT ADJUSTABLE 777 CHEVROLET Dealer A CHEVAOLET MOTOR DIVISION Gee vbi mac ER oga April 1990 Bulletin er 065001 Corporate Bulletin No Subject 4WAL BRAKE BLEEDING PROCEDURE Model and Year 1990 M L TRUCK TO ALL CHEVROLET DEALERS This bleed procedure revises the bleed procedure published in 1990 Light Duty Truck Service Manual Section 5 reference Dealer Service Bulletin No 90 65 5 This procedure is cor
8. ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE HIGH LOW VACUUM IF ENGINE IDLE IS ROUGH UNSTABLE OR INCORRECT CORRECT CONDITION BEFORE USING CHART SEE SYMPTOMS IN SECTION B ENGINE IDLING DOES SCAN TOOL DISPLAY A MAP VOLTAGE OF 4 0 VOLTS OR OVER IGNITION OFF DISCONNECT MAP SENSOR ELECTRICAL CONNECTOR IGNITION ON SCAN TOOL SHOULD READ A VOLTAGE OF 1 VOLT ORLESS DOES IT CODE 33 IS INTERMITTENT IF NO ADDITIONAL CODES WERE STORED REFER TO DIAGNOSTIC AIDS ON FACING PAGE PROBE SENSOR GROUND CIRCUIT WITH A TEST LIGHT TO BATTERY VOLTAGE TEST LIGHT SHOULD LIGHT DOES IT CKT 432 SHORTED TO VOLTAGE OR SHORTED TO CKT 416 OR FAULTY ECM PLUGGED OPEN SENSOR GROUND CIRCUIT OR LEAKING SENSOR VACUUM HOSE OR FAULTY MAP SENSOR REFER TO DIAGNOSTIC AIDS ON FACING PAGE 10 26 89 e753210 6 90 199 DRIVEABILITY AND EMISSIONS MANIFOLO ABSOLUTE PRESSURE VACUUM TO SENSOR S TO SENSOR S REFER TO SERVICE MANUAL FOR CORRECT MAP SENSOR CIRCUIT WIRING DIAGRAM ECM 5 VOLT REFERENCE MAP SIGNAL SENSOR GROUND 11 13 89 MS 8906 6E CODE 34 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE LOW HIGH VACUUN Circuit Description The Manifold Absolute Pressure MAP sensor responds to changes in manifold pressure vacuum The ECM receives this information as a signal voltage that
9. GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED m 2 gt m C U gt gt m CO U NE Chevrolet bulletins are intended for use by professional technicians NOT a do it yourselfer They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely If a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD 148D Rev 8 86 36 905 06 1990 GM PASSENGER CAR ALIGNMENT SPECIFICATIONS DEGREES FRONT WHEELS STEERING REAR WHEELS CAMBER CROSS CASTER CROSS TOTAL TOE WHEEL ANGLE CAMBER TOTAL TOE 50 A 170 0 000 30 s _ ovem 25 2 000 30 L THRUST ANGLE A 000 15 0 20 W 20 F W 000 50 A 000 15 A 000 15 ref oniy 0 30 50 0 70 4 BO 50 0 00 20 35 ret only 0 60 60 A 1 15 4 075 0 00 20 3 5 0 25 50 030 25 0 20 60 TO COLUMN Ae EC ES gt g 0 70 50 A 2 00 4 0 50 0 75 0 00 20 3
10. PROBE TERMINAL 8 CKT 432 WITH A LIGHT TO 12 VOLTS IGNITION ON SCAN SHOULD READ OVER 4 VOLTS DOES IT CKT 474 OPEN OR SHORTED TO GROUND OR FAULTY ECM 90 199 6 DISCONNECT SENSOR ELECTRICAL CONNECTOR 351 is DRIVEABILITY AND EMISSIONS CODE 64 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE LOW HIGH VACUUM CODE 64 IS INTERMITTENT IF NO ADDITIONAL CODES WERE STORED REFER TO DIAGNOSTIC AIDS ON FACING PAGE FAULTY CONNECTION OR SENSOR REFER TO DIAGNOSTIC AIDS ON FACING PAGE CKT 432 OPEN OR SHORTED TO GROUND OR CKT 432 SHORTED TO SENSOR GROUND OR FAULTY ECM 3 6 90 78 3158 6 Chevrolet TA CHEVROLET MOTOR DIVISION n Secton Genera Motors Corporation CHEVROLET Service October 1989 Service Departmen SERVICE Update Dae Date Bulletin Corporate Bulletin No Sumect REVISED PRELIMINARY CHECK PROCEDURE AND SHIFT SPEED CHART FOR 1990 4L60 700 R4 TRANSMISSIONS Model and Year 1980 PASSENGER CARS WITH 4160 TRANSMISSION 1990 LIGHT DUTY TRUCKS WITH 4L60 TRANSMISSION A We TO ALL CHEVROLET DEALERS m This bulletin provides a revised Preliminary Check Procedure and Shift Speed Chart for A 1990 HM4L60 700 R4 transmissions These charts have been updated since publication lt of the 1990 Service Manuals Please make reference
11. open or if CKT numbers on the diagnostic chart 432 1s shorted to voltage or to CKT 416 1 This step will determine if Code 33 is the result of a hard failure or an intermittent condition A Code 33 will set under the following conditions MAP signal voltage is too high low vacuum e TPS less than 2 These conditions exist longer than 5 seconds 2 This step simulates conditions for a Code 34 Ifthe ECM recognizes the change the ECM and CKT 416 and CKT 432 are OK If CKT 469 is open there may also be a stored Code 23 Diagnostic Aids With the ignition ON and the engine stopped the manifold pressure is equal to atmospheric pressure and the signal voltage will be high This information is used by the ECM as an indication of vehicle altitude Comparison of th s reading with a known good vehicle with the same sensor is a good way to check accuracy of suspect sensor Readings should be the same 4 volt 90 199 6E If Code 33 is intermittent refer to Section B NOTE Make sure electrical connector remains securely fastened s Check all connections e Disconnect sensor from bracket and twist sensor by hand only to check for intermittent connections Output changes greater than 1 volt indicates a bad connector or connection Hf OK replace sensor e Refer to CHART C 1D MAP sensor voltage output check for further diagnosis e 4 DRIVEABILITY AND EMISSIONS CODE 33 MANIFOLD
12. or holding the T V cable to the full extent of its travel and with the brakes applied take the line pressure readings in the ranges and at the engine r p m indicated in the chart below NOTICE Total running time for this combination not to exceed 2 minutes CAUTION Brakes must be applied at all times 1990 HYDRA MATIC 4L60 TRANSMISSION PRESSURES NORMAL PRESSURE NORMAL PRESSURE AT MINIMUM T V AT FULL TY _ 5 _ 6575 816 1016 118 147_ CBM MNM WAM 123 154 CUM TNM WBM 137 172 PARK CHM CJM RAM WCM 133 167 NEUTRAL 683622 7090 8831170 OVERORIVE 8 FM 451515 6575 8181146 133 168 MANUAL RFRMEM 6575 10731354 158 196 1000 RPM HMHM asa 7090 1019134 148155 162 207 PAM IBM ACM LOM LEM 451515 6575 8991134 130 164 65 75 483 622 70 90 116 157 141179 742 847 108123 1342 1670 195 242 SHM TLM BAM FTM 42847 108 123 1686 2146 245 311 CBM HCM HOM KAM MJM WAM 742 847 108 123 1400 1747 203253 COM TNM WBM 742 84 108 123 1556 1948 226 283 CHM CJM RAM TMM WCM 742847 108 123 1503 1889 218 274 108 123 793 1023 115 148 1451 1924 210 273 580 562 171214 REVERSE 1000 RPM FUM FZM HBM HJM YOM 742 847 256 323 793 1023 115 148 742847 108 123 65 340
13. the vehicle manufacturer must first deter mine that neither his safety nor the safe operation of the vehicle will be jeopardized by the replacement part ser vice procedure or tool selected It is important to note that this manual contains various Cautions and Notices that must be carefully observed in order to reduce the risk of personal injury during service or repair or the possibility that improper service or repair may damage the vehicle or render it unsafe It is also important to understand that these Cautions and Notices are not exhaustive because it is impossible to warn of all the possible hazardous consequences that might result from failure to follow these instructions may be used NOTICE When fasteners are removed always rein stall them at the same location from which they were removed a fastener needs to be replaced use the correct part number fastener for that application If the correct part number fastener is not available fastener of equal size and strength or stronger may be used Fasteners that are not reused and those requiring thread locking compound will be called out The correct torque value must be used when install ing fasteners that require it If the above conditions are not followed parts or system damage could result CHEVROLET MOTOR DIVISION General Motors Corporation WARREN MICHIGAN 1991 GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED e LITHO IN U S
14. will vary from about 1 to 1 5 volts at closed throttle idle to 4 5 4 8 volts at wide open throttle low vacuum If the MAP sensor fails the ECM will substitute a fixed MAP value and use the Throttle Position Sensor 5 to control fuei delivery Test Description Numbers below refer to circled numbers on the diagnostic chart 1 This step determines if Code 34 is the result of a hard failure or an intermittent condition Code 34 will set when MAP signal voltage is too low and the ignition is ON 2 Jumpering harness terminals B to C 5 volts to signal circuit will determine if the sensor is at fault or if there is a problem with the ECM or wiring 3 The Scan tool may not display 5 volts The important thing is that the ECM recognizes the voltage as more than 4 volts indicating that the ECM and CKT 432 are OK Diagnostic Aids intermittent open in CKT 432 or CKT 416 will result in a Code 34 With the ignition ON and the engine OFF the manifold pressure is equal to atmospheric pressure and the signal voltage will be high This information is used by the ECM as an indication of vehicle altitude 90 199 6E Comparison of this reading with a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor Readings should be the same t 4 volts Also CHART C 1D can be used to test the MAP sensor Refer to Intermittents in Section NOTE Make sure electrical con
15. 1990 DEALEH SERVICE MANUAL UPDATE BULLETIN SUPPLEMENT FOR THE 1990 CHEVROLET LIGHT DUTY TRUCK UNIT REPAIR ASTRO VAN C K PICKUP TRUCKS R V G P MODELS AND S 10 MODELS SERVICE MANUALS 7 1990 SERVICE MANUAL SUPPLEMENT This manual contains Dealer Service Update Bulletins covering service manual updates which were issued September 1989 through August 1990 Some pages may apply to prior or later model years will also be necessary to check bulletins issued after August 1990 CAUTION To reduce the chance of personal injury and or property damage the following instructions must be carefully observed Proper service and repair are important to the safety of the service technician and the safe reliable operation of all motor vehicles part replacement is necessary the part must be replaced with one of the same part number Any reference to brand names in this manual is intended merely as an example of the types of lubricants tools and materials recommended for use n all cases an equivalent or with an equivalent part Do not use areplacement part of lesser quality The service procedures recommended and described in this service manual are effective methods of performing service and repair Some of these procedures require the use of tools specially designed for the purpose Accordingly anyone who intends to use a replacement part service procedure or tool which is not recom mended by
16. A No part of this publication may be reproduced stored in any retrieval system or transmitted in any form or by any means including but not limited to electronic mechanical photocopying recording or otherwise without the prior written permission of the Chevrolet Motor Division of General Motors Corp This includes all text illustrations tables and charts Sec tion 3E 6C Bulletin Numbers 90 106 3E 90 213 5 90 269 5 90 206 6 90 199 6 90 77 7 90 89 7 90 56 8 Table Contents Subject Uheel Alignment Specifications 4WAL Brake Bleeding Procedure RWAL Brakes Controlled Idle Speed Updated Chart Revised Chart 10 Code 35 34 63 64 Revised Preliminary Check Procedure and Shift Speed Chart for 4L60 700 R4 Transmissions Revised Accumulator Spring Chart Packard 52 Way Connector identification 7 30 106 BE gt Deer o _ CHEVROLET MOTOR DIVISION Section General Motors CHEVROLET Service December 1989 Service Department __ __ Update Date 1 S Bulletin 99391 __ Corporate Bulletin No sujet WHEEL ALIGNMENT SPECIFICATIONS and Yea 1990 PASSENGER CARS AND LIGHT DUTY TRUCKS TO ALL CHEVROLET DEALERS ATTACHED FOR YOUH INFORMATION ARE THE 1990 MODEL WHEEL ALIGNMENT SPECIFICATIONS FOR ALL GM PASSENGEH CARS AND LIGHT TRUCKS COPYRIGHT 1989 CHEVROLET MOTOR DIVISION
17. ACTUATIONS OF THE DUMP VALVE DURING AN ANTILOCK STOP ss V Q MU mod Gu V s G IGNITION ON GROUND THE DIAGNOSTIC TERMINAL FROM DIAGNOSTIC CIRCUIT CHECK BRAKE LIGHT FLASHES CODE 5 e GROUND IGNITION OFF IS THE VEHICLE EQUIPPED WITH 4WD ALDL CONNECTOR DIAGNOSTIC TERMINAL ENGAGE 4WD REPLACE THE VALVE ASSEMBLY REFER TO ISOLATION DUMP VALVE IN THIS SECTION 4WD INDICATOR CHECK VOLTAGE LAMP SWITCH TERMINAL A WITH THE BRAKES APPLIED CKT 420 VERIFY OPERATION OF THE REAR BRAKES REPAIR IF NECESSARY REPAIR REFER TO TRANSFER CASE 12 VOLTS 0 VOLTS CHECK VOLTAGE AT PIN F OF THE CHECK VOLTAGE AT SINGLE CAVITY MODULE CONNECTOR CKT 420 CONNECTOR FROM TRANSFER CASE SWITCH 0 VOLTS 0 VOLTS 12 VOLTS IGNITION OFF s REMOVE THE STOP HAZARD FUSE INSTALL THE FUSE AFTER 5 SECONDS ECM B fuse on S T Series truck Stop hazard fuse on C K and PERFORM THE OIAGNOSTIC R V Series truck CIRCUIT CHECK fuse on M Series truck Tail LPS fuse on G Series truck Figure 1 90 269 5 7 CHEVROLET Dealer _ 90 206 6C Number CHEVROLET MOTOR DIVISION Gece Service 6 Bulletin we 036504 Corporate Bulletin No sujet CONTROLLED IDLE SPEED UPDATED CHART MedelandYea 1990 ALL TRUCKS EXCEPT TRACKER TO ALL CHEVROLET DEALER
18. E IRANS D N RPM COUNTS LOOP 5 7L MAN N 600 5 30 OPEN under AUTO D 525 5 30 CLOSED 8500 GVW 5 7L MAN 650 5 30 OPEN over MAN 4 N 650 5 30 CLOSED 8500 GVW AUTO D 550 5 30 CLOSED 7 4L MAN N 800 5 30 OPEN under AUTO D 750 5 30 OPEN 8500 GVW 7 41 750 5 30 AUTO D 750 5 30 OPEN 8500 GVW Add 2 counts for engines with less than 500 rniles Add 2 counts for every 1000 ft above sea level 4 3L amp V8 Add 1 count for every 1000 ft above sea level 2 5 amp 2 8L Let engine idle until proper fuel control status open closed loop is reached Switches to open loop after 3 min 1 43L S T series 2 4 3L High Output WL van series 3 3 Speed Automatic in a C10 pickup with Federal emissions and system 4 G van or Suburban with a single catalytic converter COPYRIGHT 1990 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED 90 206 6C CHEVROLET Dealer __90 199 6 Number CHEVROLET MOTOR DIVISION GGG Service dis 6E Cdp c Update March 1990 Bulletin Dale 016510 Corporate Bulletin No sume REVISED CHART C 1D CODE 33 34 63 64 Model and Year 1980 90 PASSENGER CARS AND TRUCKS TO ALL CHEVROLET DEALERS This bulletin revises the Manifold Absolute Pressure MAP Output Check Chart 10 and updates Code 33 Code 34 Code 63 and Code 64 in the Service Manual section on Driveability And Emissions
19. ER TO DIAGNOSTIC AIDS ON FACING PAGE 2 23 90 75 3157 5 90 199 6 AND EMISSIONS SENSOR TO EGR ASSEMBLY MANIFOLD ABSOLUTE PRESSURE VACUUM TO COOLANT AND MAT SENSORS TO TPS 416 GRY 474 GRY RED 432 LT GRN MAP SIGNAL 455 PPL SENSOR GNO 10 10 86 75 3093 6 CODE 64 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE LOW HIGH VACUUM Circuit Description The Manifold Absolute Pressure sensor responds to changes in manifold pressure vacuum The ECM receives this information as a signal voltage that will vary from about 1 to 1 5 volts at closed throttle 1dle to 4 5 4 8 volts at wide open throttle low vacuum If the MAP sensor fails the ECM will substitute a fixed MAP value and use the Throttle Position Sensor TPS to control fuel delivery Test Description Numbers below refer to circled numbers on the diagnostic chart 1 Code 64 will set if Engine rpm less than 600 Manifold pressure reading less than 13 kPa Conditions met for second or Engine rpm greater than 600 Throttle angle over 20 Manifold pressure less than 13 kPa Conditions met for 1 second 2 This test to see if the sensor is at fault for the low voltage or if there is an ECM or wiring problem 3 This simulates a high signal voltage to check for an open in 432 If the test light is bright during th
20. FER TO SERVICE MANUAL FOR CORRECT MAP SENSOR MAP SENSOR CIRCUIT WIRING DIAGRAM ABC TO MANIFOLD SENSOR S ABSOLUTE RESSURE TD 5 VOLT VACUUM REFERENCE x MAP SIGNAL SENSOR GROUND TO SENSOR S 11 13 89 MS 8906 6 CHART C 1D MANIFOLD ABSOLUTE PRESSURE MAP VOLTAGE OUTPUT CHECK Circuit Description The Manifold Absolute Pressure MAP sensor measures the changes in the intake manifold pressure which result from engine load intake manifold vacuum and rpm changes and converts these into a voltage output The ECM sends a 5 volt reference voltage to the MAP sensor As the manifold pressure changed the output voltage of the sensor also changes By monitoring the sensor output voltage the ECM knows the manifold pressure A lower pressure low voltage output voltage will be about 1 2 volts at idle While higher pressure high voltage output voltage will be about 4 4 8 at Wide Open Throttle WOT The MAP sensor is also used under certain conditions to measure barometric pressure allowing the ECM to make adjustments for different altitudes The ECM uses the MAP sensor to control fuel delivery and ignition timing Test Description Numbers below refer to circled 3 Check vacuum hose to sensor for leaking or numbers on the diagnostic chart restriction Be sure that no other vacuum devices are connected to the MAP hose 9 Important Be sure to use the same Diagnostic Test NOTE Make sure electrical
21. S This bulletin updates the chart shown on Page 4 43 in the Fuel Control Section of the 1990 Shop Manual This information is for all 1990 Light duty trucks except Tracker with gas engines 1990 CONTROLLED IDLE SPEED GEAR IDLE SPEED OPEN CLOSED ENGINE TRANS D N RPM COUNTS LOOP 2 90 MAN N 950 S 5 20 CLOSED AUTO D 800 S 15 40 CLOSED 750 M 2 8L MAN N 800 5 20 OPEN 3 1L AUTO D 650 5 15 CLOSED 4 3L MAN 550 2 20 CLOSED under AUTO D 537 10 25 CLOSED 8500 AUTO 1 D 500 5 30 CLOSED GVW MAN 1 N 600 5 30 CLOSED AUTO 2 D 588 10 25 CLOSED 4 3L MAN N 650 12 30 CLOSED over AUTO D 650 20 35 CLOSED 8500 GVW 5 0L MAN N 600 5 30 OPEN AUTO D 500 5 30 CLOSED 3 D 500 5 30 CLOSED B A E PPP Chevrolet bulletins are intended for use by professional technicians NOT a do it yoursaifer They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely If a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD148J Rev 12 89 o JJ O m U g gt m soe GEAR IDLE SPEED IAC OPEN CLOSED ENGIN
22. Y RED MANIFOLD ABSOLUTE 432 LT GRN PRESSURE F15 MAP SIGNAL VACUUM 7 SENSOR GND TO COOLANT AND MAT SENSORS 10 10 86 75 3093 6 63 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE HIGH LOW VACUUM Circuit Description The Manifold Absolute Pressure MAP sensor responds to changes in manifold pressure vacuum The ECM ceceives this information as a signal voltage that will vary from about 1 to 1 5 volts at closed throttle idle to 4 5 4 8 volts at wide open throttle low vacuum If the MAP sensor fails the ECM will substitute a fixed value and use the Throttle Position Sensor TPS to control fuel delivery Test Description Numbers below refer to circled Diagnostic Aids numbers on the diagnostic chart 1 Code 63 will set when With the ignition ON and the engine stopped Engine running the manifold pressure is equal to atmospheric pressure Manifold pressure greater than 75 3 kPa A C and the signal voltage will be high This information OFF 81 2 kPa A C ON is used by the ECM as an indication of vehicle altitude Throttle angle less than 2 Comparison of this reading with a known good vehicle Conditions met for 2 seconds with the same sensor is a good way to check accuracy Engine misfire or a low unstable idle may set of a suspect sensor Readings should be the same Code 63 4 volt 2 With the MAP sensor disconnecte
23. __ FEET __ __ FTM M 0218 2225 2541 2531 1421 FZM 1216 2431 4232 3646 3439 10 19 1012 Pal El 2 ss 26 28 4048 31 45 2834 1929 1215 ee mas AM CM CM Lom 1244 2126 2233 2838 1421 79 a r i uere gt ra 2028 4783 2437 3747 gt 2 3 en Es 13 18 013 2023 4046 Tu etm 3 _ _______ YE 1316 2125 ses 39 53 2228 13 19 Be EY E E NOTES 1 ALL SPEEDS INDICATED ARE IN MILES PER HOUR CONVERSION TO km h MPH x 1 609 2 SHIFT POINTS WILL VARY SLIGHTLY OUE TO ENGINE LOADS AND VEHICLE OPTIONS 3 SPEEDS LISTED WITH EXCEED 55 MPH LHOOO2 4460 82 Figure 1 90 77 PRELIMINARY CHECK PROCEDURE CHECK TRANSMISSION FLUID LEVEL 4 CHECK AND ADJUST T V CABLE CHECK OUTSIDE MANUAL LINKAGE AND CORRECT CHECK ENGINE TUNE J INSTALL PRESSURE GAGE lt ED trs CONNECT TACHOMETER TO ENGINE Oi eet CHECK PRESSURE AS FOLLOWS UPR AEA RARE N Minimum T V Lina Pressure Check Set the T V cable to specification and with the brakes applied take the ling pressure readings n the ranges and at the engine r p m indicated in the chart below Full T V Line Pressure Check Full T V line pressure readings are obtained by ty ng
24. connector remains securely fastened Equipment for all measurements 1 When comparing Scan readings to a known good vehicle it is important to compare vehicles use a MAP sensor having the same color insert or having the same Hot Stamped number See figures on facing page 2 Applying 34 kPa 10 Hg vacuum to the MAP sensor should cause the voltage to change Subtract seeond reading from the first Voltage value should be greater than 1 5 volts Upon applying vacuum to the sensor the change in voltage should be instantaneous A slow voltage change indicates a faulty sensor 4 Disconnect sensor from bracket and twist sensor by hand only to check for intermittent connection Output changes greater than 1 volt indicate bad connector or connection If OK replace sensor 90 199 6E DRIVEABILITY AND EMISSIONS CHART C 1D MANIFOLD ABSOLUTE PRESSURE MAP VOLTAGE OUTPUT CHECK NOTE THIS CHART ONLY APPLIES TO MAP SENSORS HAVING GREEN OR BLACK COLOR KEY INSERT SEE BELOW IGNITION ON ENGINE OFF SCAN TOOL SHOULD INDICATE A MAP SENSOR VOLTAGE COMPARE THIS READING WITH THE READING OF A KNOWN GOOD VEHICLE SEE FACING PAGE TEST DESCRIPTION STEP 1 VOLTAGE READING SHOULD BE WITHIN 2 4 VOLT 15 17 DISCONNECT AND PLUG VACUUM SOURCE SENSOR CONNECT A HAND VACUUM PUMP TO MAP SENSOR START ENGINE NOTE MAP SENSOR VOLTAGE APPLY 34 kPa 10 Hg OF VACUUM AND NOTE VOLTAGE CHANGE
25. d the ECM If idle is rough or unstable refer to symptoms in should see a low voltage if the ECM and wiring are Section B for items which can cause an unstable idle OK n open in CKT 455 or the connection will resuit in a Code 63 NOTE Make sure electrical connector remains securely fastened Check all connections e Disconnect sensor from bracket and twist sensor by hand only to check for intermittent connections Output changes greater than 1 volt indicates a bad connector or connection If OK replace sensor e Refer to CHART C 1D MAP sensor voltage output check for further diagnosis 90 199 6 AND EMISSIONS CODE 63 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE HIGH LOW VACUUM IF ENGINE IDLE IS ROUGH UNSTABLE OR INCORRECT CORRECT BEFORE USING CHART SEE SYMPTOMS IN SECTION B ENGINE IDLING DOES SCAN TOOL DISPLAY A MAP VOLTAGE OF 4 0 VOLTS OR OVER IGNITION OFF CODE 63 15 INTERMITTENT DISCONNECT MAP SENSOR ELECTRICAL CONNECTOR IF NO ADOITIONAL CODES WERE IGNITION ON STORED REFER TO DIAGNOSTIC SCAN SHOULD READ A VOLTAGE OF 1 VOLT OR LESS AIDS ON FACING PAGE DOES IT PROBE CKT 455 WITH A TEST LIGHT TO 12 VOLTS CKT 432 SHORTED TO VOLTAGE e TEST LIGHT SHOULD LIGHT OR DOES IT SHORTED TO CKT 474 OR FAULTY PLUGGED OPEN CKT 455 OR LEAKING SENSOR VACUUM HOSE OR FAULTY MAP SENSOR REF
26. is test 432 is probably shorted to ground If Scan reads over 4 volts at this test CKT 474 can be checked by measuring the voltage at terminal C should be 5 volts 90 199 Diagnostic Aids An intermittent open in CKTs 432 or 474 will result in a Code 64 With the ignition ON and the engine OFF the manifold pressure is equal to atmospheric pressure and the signal voltage will be high This information is used by the ECM as an indication of vehicle altitude Comparison of this reading with known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor Readings should be the same t 4 volts Also CHART C 1D can be used to test the MAP sensor Refer to Intermittents in Section p NOTE Make sure electrical connector remains securely fastened Check all connections Disconnect sensor from bracket and twist sensor By hand only to check for intermittent connections Output changes greater than volt indicates a bad connector or connection If OK replace sensor Refer to CHART 10 MAP sensor voltage output check for further diagnosis IGNITION OFF FOR 10 SECONDS START ENGINE AND IMMEDIATELY NOTE MAP VALUE ON SCAN DOES SCAN DISPLAY MAP BELOW 25 VOLT IGNITION OFF JUMPER HARNESS TERMINALS B TO C IGNITION MAP VOLTAGE SHOULD READ OVER 4 7 VOLTS DOES IT IGNITION OFF REMOVE JUMPER WIRE
27. nector remains securely fastened Check all connections Disconnect sensor from bracket and twist sensor By hand only to check for intermittent connections Output changes greater than 1 volt indicates a bad connector or connection If OK replace sensor Refer to CHART C 1D MAP sensor voltage output check for further diagnosis DRIVEABILITY AND EMISSIONS CODE 34 MANIFOLD ABSOLUTE PRESSURE MAP SENSOR CIRCUIT SIGNAL VOLTAGE LOW HIGH VACUUM ENGINE IDLING DOES SCAN TOOL DISPLAY MAP VOLTAGE BELOW 25 VOLT IGNITION OFF DISCONNECT SENSOR ELECTRICAL CONNECTOR JUMPER HARNESS TERMINALS 787 TO C IGNITION ON MAP VOLTAGE SHOULD READ OVER 4 7 VOLTS DOES IT CODE 34 15 INTERMITTENT IF NO ADDITIONAL CODES WERE STORED REFER TO DIAGNOSTIC AIDS ON FACING PAGE IGNITION OFF REMOVE JUMPER WIRE IGNITION PROBE TERMINAL B MAP SIGNAL WITH A TEST LIGHT TO BATTERY VOLTAGE SCAN TOOL SHOULD READ OVER 4 VOLTS DOES IT FAULTY CONNECTION OR SENSOR REFER TO DIAGNOSTIC AIDS ON FACING PAGE 5 VOLT REFERENCE CIRCUIT OPEN CKT 432 OPEN OR OR SHORTED TO GROUND CKT 432 SHORTED TO GROUND OR OR FAULTY ECM CKT 432 SHORTED TO SENSOR GROUND OR FAULTY ECM 10 29 89 e 75 3211 6E 90 199 6 DRIVEABILITY AND EMISSIONS MAP SENSOR TO EGR ASSEMBLY TO TPS 416 GRY 474 GR
28. o a job properly and safely condition is described DO NOT assume thatthe bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer for information on whether your vehicle may benefit from that information GSD148J Rev 12 89 25 IMPORTANT The EHCU module should be bled after replacement or if trapped air is 10 11 12 TS 14 thought to be in the unit It should not be necessary to bleed the EHCU module if the fluid has not become contaminated or if no air is thought to be in the module In the event the EHCU module needs to be bled the module should be thoroughly bled BEFORE wheel cylinders and calipers There are two bleeders on the front of the unit that look like normal brake bleeders Figure 2 These are the modulator bleeders for bleeding the EHCU module and they must remain closed when the unit is not pressur ized EHCU Module Bleed Procedure if required Pedal bleeding method described below Slowly depress the brake pedal one time and hold Open one of the modulator bleeders on the front of the unit until fluid flows clearly or pedal is depressed e Close the modulator bleeder and tighten to 7 Nm 60 5 DO NOT OVER TIGHTENI Slowly release the pedal Wait 15 seconds then repeat the above sequence including the 15 second wait until all air is purged from the EHCU module Hepeat the above process on the remaining modula
29. on that indicates any of these colors as being C amp D connectors found in the 6E and 8D Sections of the affected Service Manuals LL XJ LL C 79 O E m COPYRIGHT 1989 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED mu o UM rr sss sua Chevrolet bulletins are intended for use by professional technicians NOT a do it yourselfer They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job property and safely if a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealer tor information on whether your vehicle may benefit from that information GSD 1480 Rev 8 86 STRAIN RELIEF 2 CONNECTOR END 90 56 8 7 CHEVROLET
30. rectly listed in the 1991 S T service manual as it applies to that model Please place a copy of this bulletin in the 1990 Light Duty Truck Service Manual The following brake bleeding procedure is to be used on ALL 1990 M L Vans equipped with 4 wheel anti lock brake systems IMPORTANT The ignition switch must be off through out bleeding or false trouble codes could be set to memory 4WAL Brake System Bleeding Procedure Y m E m 79 O gt m 1 Assure ignition is in off position 2 Deplete brake booster by pumping the brake pedal several times 3 Assure the master cylinder is full 4 Install two j 35856 bleed valve tools on the 4WAL EHCU at the high pressure accumulators HPA see Figure 2 5 Install one J 35856 bleed valve tool on the combination valve 6 There are internal bleed screws on each side of the EHCU module Figure 2 The bleed screws are used to open the internal passages within the EHCU module Back off the two internal bleed screws 1 4 to 1 2 turn 7 Use conventional bleeding process Pressure Vacuum Pedal Bleeding Chevrolet bulletins are intended for use by professional technicians NOT do it yourselfar They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to d
31. to these changes in your service C manuals m C 70 U COPYRIGHT 1989 gt CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION m ALL RIGHTS RESERVED RE Chevrolet bulletins are intended for use by professional technicians NOT a do it yourselfer They are written to inform these technicians of conditions that may occur on some vehicles or to provide information that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools safety instructions and know how to do a job properly and safely If a condition is described DO NOT assume that the bulletin applies to your vehicle or that your vehicle will have that condition See your Chevrolet dealerfor information on whether your vehicle may benefit from that information GSD 148D Rev 8 86 1990 HYDRA MATIC 4160 SHIFT SPEED CHART _ r 37 51 29 36 1624 1012 HM a 40 9 28 1 33 1322 QN re ee te THROTTLE THROTTLE THROTTLE DOWN DOWN a a HON AA BM 13 16 22 27 50 29 43 48 1320 9 311 1418 263 4052 31 48 29 33 1724 10 12 MJM WAM 14 18 24 42 37 48 11 14 CCM KBM WBM 16 19 25 31 50 33 46 12 14 CHM CJM KCM RAM WCM 46 53 29 41 34 45 1521 1013 e SEC l 14318 2731 38 51 31 43 28 33 18 24 h gt _ RM ________
32. tor bleeder on the front of the EHCU module until all air is purged from the unit Always maintain a full master cylinder Bleed wheel cylinders and calipers as described in HYDRAULIC BRAKES Sec 5A of the service manual Remove the three 35856 bleed valve tools Close the left internal bleed screw and tighten to 7 Nm 60 in lbs DO NOT OVER TIGHTEN Close the right internal bleed screws and tighten to 7 Nm 60 in Ibs DO NOT OVER TIGHTEN Start vehicle and evaluate the brake pedal feel If firm continue with this procedure If the pedal is soft or spongy reinstall tools and re bleed the system starting with step 1 Any RE BLEED due to soft or spongy pedal should always include bleeding the EHCU module step 90 213 5 193 15 Pertorm 3 function tests using Tech 1 Function test procedure 16 Road test vehicle IMPORTANT Failure to follow this procedure accurately may result in an immediate soft pedal after the first anti lock stop and technician induced stored codes COPYRIGHT 1990 CHEVROLET MOTOR DIVISION GENERAL MOTORS CORPORATION ALL RIGHTS RESERVED 90 213 5 Internal Bleed Screw Left Side of EHCU Right Side Opposite Modulator Bleeders 2 22 EHCU Module T s E NU CL NR o 1 OF ee 3 ww lt lt lt An J o o 22 yn HPA Pins Figure 2 AWAL EHCU Service Bleed Valves 90 213 5 CHEVROLET Dealer
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