Honda Code Breaker
Contents
1. The four wire oxygen sensor still uses the same 0 5 volt bias voltage on the oxygen sensor signal wire If we monitor that voltage with the key on and the heater activated we should see 0 4 0 5 volts just as the key is turned on That voltage should slowly fall to less than 0 1 volts within two minutes If the engine is not running there should be 21 percent 0 in the exhaust manifold which would make an 0 sensor read very low If the value stays at 0 5 volts and drops very slowly or not at all replace the 02 sensor Seven Wire Oxygen Sensor Systems Code 48 P1162 P1168 P1169 The seven wire system is actually a linear air fuel ratio sensor rather than an oxygen sensor in the tra ditional sense Using this sensor as an input the ECU can control the fuel mixture at 14 7 to 1 for most driving conditions or at 22 to 1 for optimal fuel economy under ideal conditions This sensor uses multiple heaters and the book tests don t real ly give any insight as to what s occurring as far as tangible values In most cases replacement of the sensor is required if a problem is detected Sensor replacement may become necessary with as little as 30 000 miles on the vehicle March 1999 IMPORT SERVICE Honda Code Breaker international Automotive Technicians Network The International Automotive Technicians Network is a group of 18 727 professional automotive technicians from all over the world The automotive technician mem2. This occurs when when the roll pin that secures the CYL TDC reluctor to the distributor shaft rusts away The reluctor may not spin with the distributor shaft but the pickup coil for the igniter in the top of the distributor still functions producing its signal The sensors test fine with an ohmmeter but produce no AC signal because there is no reluctor movement Turn the key on then hold a heavy duty trigger type soldering gun next to the base of the distributor If the magnetic pulse of the soldering gun causes the injectors work but they do not work when you crank the engine replace the distributor as a unit Later models use two or three sensors integral with the distributor Again if one sensor reads 400 ohms they should all read 400 ohms In most cases the sensor if separate such as the CYL sensor on Preludes or distributor needs replacing if these codes are set Refer to the article on Honda ignition systems in the November 1998 Import Service for more information on this Code 9 very often appears after replacing the timing belt on 1988 1989 Prelude models and also the 1988 89 Acura Integra There are two sensors in the dis tributor CRK and TDC and one CYL sensor driven by the exhaust camshaft The ECU knows when these sig nals should occur in relation to each other The CRK and TDC sensors are both in the distributor so they are unlikely to get out of time But if the cam belt is incor rectly installed or jumps a t
3. 1999 Figure 8 The intake air temperature TA sensor is attached to the intake manifold arrow This one uses the same green harness con nector also found on the coolant temperature TW sensor Voltage readings from both sensors should match when the engine is cold Intake Air Temperature TA Sensor Code 10 P0112 Low Input P0113 High Input The TA Sensor is usually located on the intake manifold and uses two wires just like the TW sen sor a signal wire usually R Y which has a 5 volt reference and a ground G W or Br B On early models a Code 10 was expressed as ten quick flashes on later models it s one long flash If you re not sure whether you re seeing a Code 1 or a Code 10 later models unplug the 02 sensor with the key on to see how long a Code 1 takes Was it the same quick flash or a slower one If the engine is cold or has been sitting for a long while the TW sensor and TA sensor should read the same voltage with the key on plugged in On 1990 1993 Accords the TA sensor connector is very close to and interchangeable with the power steering pressure sensor If a Code 10 appears look for signs of body work or an engine swap The PS pressure switch on the PS pressure hose has solid color wires red and black Time Out A little knowledge can be dangerous But too much knowledge can give you a headache Honda diagnostic trouble codes are the key to a great deal of useful information as the length
4. of this multi part article indicates I appreciate your patience for sticking with me so far We ve got one more install ment to go before we re finished with Honda s diag nostic trouble code system See you then E By Marlowe Peterson 31
5. PF IMPORT SERVICE Honda Breaker part two Fuel Injected Hondas Codes Retrieval Methods Real World Diagnoses Service we covered ECU locations and explained how to recover diagnostic trouble codes DTC s from Honda engine management systems This month we ll discuss exactly what the codes mean explain why and how a code can set and identify the high percentage repair that will usually fix the car Keep in mind I used the word usually It s difficult to make accurate generalizations so it is impossible to name the actual cause of every pos sible DTC In other words there is no substitute for actual testing Hondas are generally predictable but I wouldn t bet the farm on a hunch or on what hap pened yesterday If you ve tried my suggestions and still have a problem get the meters out and run the voltage tests You ll fix the car right and you ll learn something too our last installment February 1999 Import Single Wire Oxygen Sensor Systems Codes 1 And 2 Code 1 or 2 indicate an out of range signal has been received from the 0 sensor Code 2 is used only on systems with two 02 sensors in the exhaust manifold If both oxygen sensors were replaced and the lead wires were switched on the two sensors the car may run poorly until the CHECK ENGINE or 24 PGM FI light comes on then run fine in open loop or limp home mode If that is the symptom check to see that the sensors are plugge
6. and about 3 0 4 0 on a very cold engine It should never read 0 or 5 volts when plugged in these extremes will set a code In the case of a hot restart complaint warm the engine to operating temperature monitoring the TW sensor voltage Shut off the engine then restart the engine while watching your voltmeter as you crank the engine after waiting five minutes It should still be around 0 5 0 6 volts If it shot up to 3 8 volts or so and the engine floods long injector pulse replace the coolant sensor In most cases Code 6 requires replacement of the TW sensor Figure 6 The coolant TW sensor is right next to the cooling fan sensor on this early PGM FI Accord Their harness connectors are interchangeable which can lead to problems The green har ness connector closest to the valve cover is attached to the coolant sensor March 1999 IMPORT SERVICE ii S WE ii ki Figure 7 The throttle position sensor is attached to one end of the throttle shaft One of the headless anti tamper screws is visible at the top of this sensor arrow Careful work with a sharp punch will usually loosen these screws if adjustment is necessary Space is at a premium at the bottom of the sensor Throttle Position Sensor TPS Code 7 P0122 low input P0123 high input The throttle position sensor is in line with the throttle shaft on the throttle body The TPS is a three wire sensor with a 5 volt reference a ground and a signal wir
7. bers of this group exchange technical knowledge and information with fellow iATN members The combined knowledge of thousands of top industry professionals networking together helps the professional members of this group to provide the highest quality automotive repair diagnosis and service in the world Figure 2 The plastic cover has been removed to get a glimpse of the MAP sensor and other EFI related components mounted If you are a professional automotive technician inside the control box on this early Accord PGM FI model and would be interested in networking with other Manifold Air Pressure Sensor automotive professionals from all over the world Codes 3 P0107 P0108 point your browser to 5 P0106 http www iatn net a EE E eae 7 HW find i i e sensors are located in the black box on the where you wilr ind tan Membership firewall on early models and bolted directly on top of Information and Requirements the intake manifold on some later models The hose to AINM Ono Eeee a MAP sensor is always numbered 21 unless it s To promote the continued growth success and image of the Professional irectly mounted to the top of the intake manifold Code 3 indicates an electrical malfunction of the MAP sensor There are three wires to Honda MAP sensors a 5 volt reference a ground and a signal wire The signal wire should read about 2 9 volts with the key on and drop to about 0 8 volts at idle with 20 21 inches of manifold vacuum If t
8. d in correctly Cylinders 1 and 4 are feedback paired with the A oxygen sensor while cylinders 2 and 3 are feedback paired with the B sensor Code 2 could be caused by a leaking injector and if that injector were now switched to either number 1 or 4 cylinder triggering Code 1 that could help verify the problem injector Figure 1 Early models use a single wire zirconia oxygen sensor Things got more complicated with later four and seven wire sen sors and multiple sensors March 1999 IMPORT SERVICE Honda Code Breaker 0 sensor activity or lack of it is what sets the code The parameters the ECU is looking for are the 0z sensor voltage should be over 0 6 volts under WOT conditions and under 0 4 volts during closed throttle decel At other throttle angles a good 02 sensor may crosscount as often as three times per second if viewed on a scope with the engine speed at approximately 3000 rpm If the TPS is set correctly your meter may show 0 0 volts briefly as the engine decels in fuel cut mode closed throttle above 1200 rpm after snap ping the throttle open There is approximately a 0 5 volt bias on the signal wire from the 0 sensor to the ECU With the 0 sensor unplugged the value on the harness side of the connector should read approximately 0 5 volts with the key on If it reads 0 0 volts unplug the ECU and check the wire for continuity to ground if none is present secure the connection at the ECU If i
9. e Typically the signal is 0 48 0 50 volts with the throttle closed and goes to about 4 5 volts at wide open throttle It should never read either 0 0 or 5 0 volts The TPS is not replaceable without buying the complete throttle assembly The heads of the screws holding the TPS in place shear off during installation To attempt adjustment a punch may be used to loosen the screws Then replace them with standard Phillips or hex head screws Adjustment will never correct a code unless someone has already moved it way out of whack before you When setting base idle on a 1988 91 Civic SPFI you will note that at 0 51 volts on the R L signal wire the top injector will start clicking The top injector should not click at idle If it does moni tor the TPS voltage when setting base idle It should be around 0 48 0 50 volts at 600 rpm with the EACV unplugged A reading of less than 0 51 volts is more important than an engine speed of exactly 600 rpm If the TPS output voltage is too high over 0 6 volts at idle it may prevent the Shift Interlock system from operating The Shift Interlock system will not operate the lock solenoid on the shifter unless the brake pedal is depressed It will also not operate the solenoid if it thinks you have the throttle open pedal misapplica tion If TPS voltage is over 0 6 volts check for a car bon buildup on the throttle blade before attempting to adjust the TPS or condemning any parts IMPORT SERVICE March
10. electric heater however There is a 12 volt key on supply voltage to the 26 sensor and the sensor ground is controlled by the ECU The two wires on the sensor side of the con nector correspond to heater power and ground These wires are usually black If a Code 41 appears four long flashes and one short flash at the end check the two black wires on the 0 sen sor side of the connector for continuity Typically you ll find a 20 40 ohm reading on a good heater circuit If the sensor circuit is open replace the 02 sensor Code 1 indicates an oxygen sensor problem while the service manual calls Code 43 a fuel system code There s no explanation why the ECU sets a Code 43 instead of a Code 1 For Code 43 the man ual instructs you to look for things like leaking injectors etc which could also cause a Code 1 Don t worry about what number is displayed The ECU just told you it doesn t like the 02 sensor so we ll leave it at that The nice thing about heated 0 sensors is the car doesn t have to be running to see what s what This heater can get the oxygen sensor warm enough to recreate a driven warmed up vehicle condition Unplug the 0 sensor connector and check with the key on and a test light for the twelve volt power source usually a B Y or Y B wire Now with the sensor plugged in ground the other wire in the connector that corresponds to the other black wire of the 02 sensor This will turn the heating element on
11. he out put voltage reads as it should at the sensor check the output wire right at the ECU A signal of near zero volts or over 4 0 volts sets the code Code 5 indicates a problem with the vacuum circuit This means the ECU is receiving the correct voltage values but they are not changing If the MAP sensor hose is cut this code will set because the output value did not change once the engine was started Damaged MAP sensor hoses where it attaches at the throttle body are a common occurrence on 1988 91 Civics A code could be set if the TPS shows a closed throttle voltage with an idle rpm value but the ECU sees 2 9 volts from the MAP sensor The small ori fice in the MAP sensor where the hose attaches may clog If the MAP sensor bolts to the intake manifold a carbon buildup may clog the opening On models with the MAP sensor on the intake man ifold the TPS connector and MAP connector have the same configuration and the harness connectors may be switched While this may not set a code because the voltages will still be within normal operating parameters it will sure cause a driveability problem Look for this error if engine work has been done and you can t identify a driveability problem Automotive Technician by providing a forum for the exchange of knowledge and the promotion of education professionalism and integrity 28 March 1999 IMPORT SERVICE Figure 3 The bottom half of this distributo
12. ooth the ECU will recog nize the CYL sensor is no longer in sync with the CRK and TDC sensors If the code was not there before tim ing belt replacement the likely cause is a cam belt that is off by one or more teeth between the intake and exhaust cams Recheck the timing belt installation If a car comes in with a broken timing belt always remove the distributor to see whether it spins by hand If the top bearing has frozen it is very capa ble of snapping the cam belt 30 Coolant Sensor TW Code 6 P0117 Low Input P0118 High Input The coolant sensor is under the distributor on most models On 1985 89 Accords and 1985 87 Preludes it s on top of the thermostat housing and it s the sensor closest to the valve cover It unfortunately has the same size and shape con nector read easily confused as the coolant fan timer temperature sensor right next to it The sen sors however are not interchangeable The TW sensor is a negative temperature coefficient sen sor while the fan timer sensor is an open closed switch Switching the sensor connectors will set Code 6 Coolant sensors are very hard to catch in the act of failing Common complaints are a hard hot restart or the engine will not restart at all The coolant sensor has a 5 volt reference from a R W or Y G signal wire depending on year and model and a Br B or G W ground wire When the engine is fully warmed up there should be about 0 5 volts on the signal wire
13. r has been disassem bled to reveal the CYL and TDC reluctors A no start condition may be caused by a rusted roll pin that secures the reluctors to the shaft These parts are not available separately Crank Angle Sensor CRK Codes 4 P0335 P0336 8 P1359 Open P1361 1362 Top Dead Center Sensor TDC Code 9 P1381 P1382 Cylinder Position Sensor CYL On 1985 89 Accords 1985 87 Preludes and Civics through 1987 this sensor is built into the base of the distributor The four wire connector has very a distinctive terminal arrangement Two vertical terminals serve one sensor and the two remaining horizontal terminals in a straight line are connected to the other sensor These are perma nent magnet signal generators They have a resistance value of 300 1000 ohms depending on the year and model and pro duce at least 200 mv AC when the engine is running If one sensor spec is 500 ohms the other should be the same value These early sys tems may exhibit a Figure 4 CYL and TDC wiring har no start condition ness connector The two terminals The engine will have facing toward each other are con no injector pulse nected to the TDC sensor the but will have spark others to the CYL sensor IMPORT SERVICE March 1999 Honda Code Breaker Figure 5 The permanent magnet CYL and TDC sensors inside the lower half of the distributor are electrically identical and should both produce the same resistance reading
14. t reads high check for a poor ground at the ECU 1986 1987 CRX Si and Civic Si systems may set Code 1 from an unusually high quantity of fuel vapors purged from the charcoal canister during cruise conditions While this might be construed as emissions tampering a Honda motorcycle carbure tor main jet Honda P N 2466555 inserted in the braided red purge hose at the top of the throttle body effectively meters the volume of canister purge to a manageable rate At cruise conditions the 02 voltage should be neither unusually high which could indicate overfueling or too low which could be caused by clogged injectors or low fuel pressure Backprobe the 0 sensor wire using care not to also pierce the shield then drive the car You should see the 0 sensor voltage rise and fall under accel and decel conditions respectively and crosscount at idle and cruise conditions Oil or coolant contamination on the atmospheric port of the 02 sensor may kill the sensor If a visual examination shows oil or any other contaminant at the oxygen sensor repair the contaminant source and replace the sensor Coolant may wick down from the ground attachment point at the thermostat housing toward the 0 sensor Repair the leak and replace the sensor Four Wire Oxygen Sensor Systems Codes 1 P0131 P0132 41 P0135 P1166 P1167 43 Code 1 and 43 are basically the same as the oxy gen sensor codes on the single wire systems The four wire sensors use an
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