I've noticed that there are a lot of members here asking about the meanings of codes they get during diagnostics and unfortunately not a lot of members have the answer. So, as a member of this great forum, I'd like to contribute the list I have from a manual that I own. I hope this helps

CARBURETED ENGINES

CODE 12: No distributor reference pulses to the ECM. This code is not stored in memory and will only flash while the trouble exists. This code is normal when the ignition is switched ON with the engine not running.
CODE 13: Oxygen sensor circuit. The engine must operate for up to 5 minutes at part throttle, under road load, before the code will be set.
CODE 14: Shorted coolant sensor circuit. The engine must operate for up to 5 minutes before this code will be set.
CODE 15: Open coolant sensor circuit. The engine must operate for up to 5 minutes before this code will be set.
CODE 21: Throttle position sensor circuit. The engine must operate for at least 25 seconds at curb idle speed before this code will be set.
CODE 23: Mixture control solenoid circuit is shorted or open.
CODE 34: Vacuum sensor circuit. The engine must operate for up to 5 minutes at curb idle speed before this code will be set.
CODE 41: No distributor reference pulses to the ECM at the specified engine manifold vacuum. This code will be stored in memory.
CODE 42: Electronic Spark Timing (EST) bypass circuit or EST circuit has short circuit to ground or an open circuit.
CODE 44: Lean exhaust indication. The engine must operate for up to 5 minutes, be in closed loop operation and at part throttle before this code will be set.
CODE 44 & 45: If these two codes appear at the same time, it indicates a problem in the oxygen sensor circuit.
CODE 45: Rich exhaust indication. The engine must operate for up to 5 minutes, be in a closed loop and at part throttle before this code will be set.
CODE 51: Faulty calibration unit (PROM) or installation. It requires up to 30 seconds for this code to be set.
CODE 54: Mixture Control (MC) solenoid circuit is shorted or the ECM is faulty.
CODE 55: Voltage reference has short circuit to ground (terminal 21), faulty oxygen sensor or faulty ECM.

FUEL INJECTED ENGINES

Except 1991 and Later Models

Code 1000-Ignition line low.
Code 1001-Ignition line high.
Code 1002-Oxygen heater line.
Code 1004-Battery voltage low.
Code 1005-Sensor ground line out of limits.
Code 1010-Diagnostic enable line low.
Code 1011-Diagnostic enable line high.
Code 1012-MAP line low.
Code 1013-MAP line high.
Code 1014-Fuel pump line low.
Code 1015-Fuel pump line high.
Code 1016-Charge air temperature sensor low.
Code 1017-Charge air temperature sensor high.
Code 1018-No serial data from the ECU.
Code 1021-Engine failed to start due to mechanical, fuel, or ignition problem.
Code 1022-Start line low.
Code 1024-ECU does not see start signal.
Code 1025-Wide open throttle circuit low.
Code 1027-ECU sees wide open throttle.
Code 1028-ECU does not see wide open throttle.
Code 1031-ECU sees closed throttle.
Code 1032-ECU does not see closed throttle.
Code 1033-Idle speed increase line low.
Code 1034-Idle speed increase line high.
Code 1035-Idle speed decrease line low.
Code 1036-Idle speed decrease line high.
Code 1037-Throttle position sensor reads low.
Code 1038-Park/Neutral line high.
Code 1040-Latched B+ line low.
Code 1041-Latched B+ line high.
Code 1042-No Latched B+ 1/2 volt drop.
Code 1047-Wrong ECU.
Code 1048-Manual vehicle equipped with automatic ECU.
Code 1049-Automatic vehicle equipped with manual ECU.
Code 1050-Idle RPM's less than 500.
Code 1051-Idle RPM's greater than 2000.
Code 1052-MAP sensor out of limits.
Code 1053-Change in MAP reading out of limits.
Code 1054-Coolant temperature sensor line low.
Code 1055-Coolant temperature sensor line high.
Code 1056-Inactive coolant temperature sensor.
Code 1057-Knock circuit shorted.
Code 1058-Knock value out of limits.
Code 1059-A/C request line low.
Code 1060-A/C request line high.
Code 1061-A/C select line low.
Code 1062-A/C select line high.
Code 1063-A/C clutch line low.
Code 1064-A/C clutch line high.
Code 1065-Oxygen reads rich.
Code 1066-Oxygen reads lean.
Code 1067-Latch relay line low.
Code 1068-Latch relay line high.
Code 1070-A/C cutout line low.
Code 1071-A/C cutout line high.
Code 1073-ECU does not see speed sensor signal.
Code 1200-ECU defective.
Code 1202-Injector shorted to ground.
Code 1209-Injector open.
Code 1218-No voltage at ECU from power latch relay.
Code 1220-No voltage at ECU from EGR solenoid.
Code 1221-No injector voltage.
Code 1222-MAP not grounded.
Code 1223-No ECU tests run.

1991-95 Models

Code 88-Display used for start of test.
Code 11-Camshaft signal or Ignition signal-no reference signal detected during engine cranking.
Code 12-Memory to controller has been cleared within 50-100 engine starts.
Code 13-MAP sensor pneumatic signal-no variation in MAP sensor signal is detected or no difference is recognized between the engine MAP reading and the stored barometric pressure reading.
Code 14-MAP voltage too high or too low.
Code 15-Vehicle speed sensor signal-no distance sensor signal detected during road load condition.
Code 16-Knock sensor circuit-Open or short has been detected in the knock sensor circuit.
Code 16-Battery input sensor-battery voltage sensor input below 4 volts with engine running.
Code 17-Low engine temperature-engine coolant temperature remains below normal operating temperature during vehicle travel; possible thermostat problem.
Code 21-Oxygen sensor signal-neither rich or lean condition is detected from the oxygen sensor input.
Code 22-Coolant voltage low-coolant temperature sensor input below the minimum acceptable voltage/Coolant voltage high-coolant temperature sensor input above the maximum acceptable voltage.
Code 23-Air Charge or Throttle Body temperature voltage HIGH/LOW-charge air temperature sensor input is above or below the acceptable voltage limits.
Code 24-Throttle Position sensor voltage high or low.
Code 25-Automatic Idle Speed (AIS) motor driver circuit-short or open detected in 1 or more of the AIS control circuits.
Code 26-Injectors No. 1, 2, or 3 peak current not reached, high resistance in circuit.
Code 27-Injector control circuit-bank output driver stage does not respond properly to the control signal.
Code 27-Injectors No. 1, 2, or 3 control circuit and peak current not reached.
Code 31-Purge solenoid circuit-open or short detected in the purge solenoid circuit.
Code 32-Exhaust Gas Recirculation (ERG) solenoid circuit-open or short detected in the EGR solenoid circuit/EGR system failure-required changed in fuel/air ratio not detected during diagnostic test.
Code 33-Air conditioner clutch relay circuit-open or short detected in the air conditioner clutch relay circuit. If vehicle doesn't have air conditioning ignore this code.
Code 34-Speed control servo solenoids or MUX speed control circuit HIGH/LOW-open or short detected in the vacuum or vent solenoid circuits or speed control switch input above or below allowable voltage.
Code 35-Radiator fan control relay circuit-open or short detected in teh radiator fan relay circuit.
Code 35-Idle switch shorted-switch input shorted to ground-some 1993 vehicles.
Code 37-Part Throttle Unlock (PTU) circuit for torque converter clutch-open or short detected in the torque converter part throttle unlock solenoid circuit.
Code 37-Baro Reed Solenoid-solenoid does not turn off when it should.
Code 37-Shift indicator circuit (manual transaxle).
Code 41-Charging system circuit-output driver stage for generator field does not respond properly to the voltage regulator control signal.
Code 42-Fuel pump or no Autoshut-down (ASD) relay voltage sense at controller.
Code 43-Ignition control circuit-peak primary circuit current not respond properly with maximum dwell time.
Code 43-Ignition coil #1,2, or 3 primary circuits-peak primary was not achieved within the maximum allowable dwell time.
Code 44-Battery temperature voltage-problem exists in the PCM battery temperature circuit or there is an open or short in the engine coolant temperature circuit.
Code 44-Fused J2 circuit in not present in the logic board; used on the signal engine module controller system.
Code 44-Overdrive solenoid circuit-open or short in overdrive solenoid circuit.
Code 46-Battery voltage too high-battery voltage sense input above target charging voltage during engine operation.
Code 47-Battery voltage too low-battery voltage sense input below target charging voltage.
Code 51-Air/fuel at limit-oxygen sensor signal input indicates LEAN air/fuel ration condition during engine operation.
Code 52-Air/fuel at limit-oxygen sensor signal input indicates RICH air/fuel ration condition during engine operation.
Code 53-Internal controller failure-internal engine controller fault condition detected during self test.
Code 54-Camshaft or (distributor sync.) reference circuit-No camshaft position sensor signal detected during engine rotation.
Code 55-End of message.
Code 61- Baro read solenoid-open or short detected in the baro read solenoid circuit.
Code 62-EMR mileage not stored-unsuccessful attempt to update EMR mileage in the controller EEPROM.
Code 63-EEPROM write denied-unsuccessful attempt to write to an EEPROM location by the controller.
Code 64-Flex fuel sensor-Flex fuel sensor signal out of range-(new in 1993)-CNG Temperature voltage out of range-CN gas pressure out of range.
Code 66-No CCD messages or no BODY CCD messages or no EATX CCD messages-messages from the CCD bus or the body CCD or the EATX CCD were not received by the PCM.
Code 76-Ballast bypass relay-open or short in fuel pump relay circuit.
Code 77-Speed control relay-an open or short has been detected in the speed control relay.
Code 88-Display used for start of test.
Code Error-Fault code error-Unrecognized fault ID received by DRBII.

1996 and Later Models

P0107-Manifold absolute pressure/barometric pressure circuit low input
P0108-Manifold absolute pressure/barometric pressure circuit high input
P0112-Intake air temperature circuit low input
P0113-Intake air temperature circuit high input
P0117-Engine coolant temperature circuit low input
P0118-Engine coolant temperature circuit high input
P0121-Throttle/pedal position sensor/switch A circuit range/performance problem
P0122-Throttle/pedal position sensor/switch A circuit low input
P0123-Throttle/pedal position sensor/switch A circuit high input
P0125-Insufficient coolant temperature for closed loop fuel control
P0129-Catalyst monitor slow O2 sensor (Bank no. 1 Sensor no. 2)
P0131-Left bank and upstream O2 sensor voltage shorted to ground
P0132-Left upstream O2 sensor shorted to voltage
P0133-Upstream O2 sensor circuit slow response (Bank no. 1 Sensor no. 1)
P0135-O2 sensor heater circuit malfunction (Bank no.1 Sensor no. 1)
P0137-Left bank downstream or downstream and pre-catalyst O2 sensor voltage shorted to ground
P0138-Left bank downstream or downstream and pre-catalyst O2 sensor shorted to voltage
P0141-Downstream, left bank downstream or pre-catalyst O2 sensor heater failure
P0152-Left upstream O2 sensor slow response
P0162-Charging system voltage too low
P0171-Right rear (or just) fuel system too lean
P0172-Left bank or fuel system too rich
P0201-Injector no. 1 control circuit
P0202-Injector no. 2 control circuit
P0203-Injector no. 3 control circuit
P0204-Injector no. 4 control circuit
P0205-Injector no. 5 control circuit
P0206-Injector no. 6 control circuit
P0207-Injector no. 7 control circuit
P0208-Injector no. 8 control circuit
P0300-Random/multiple cylinder misfire detected
P0301-Cylinder no. 1-Misfire detected
P0302-Cylinder no. 2-Misfire detected
P0303-Cylinder no. 3-Misfire detected
P0304-Cylinder no. 4-Misfire detected
P0305-Cylinder no. 5-Misfire detected
P0306-Cylinder no. 6-Misfire detected
P0307-Cylinder no. 7-Misfire detected
P0308-Cylinder no. 8-Misfire detected
P0320-No crank reference signal PCM
P0340-No cam signal at PCM
P0351-Ignition coil no. 1 primary circuit
P0420-Left bank catalytic converter or just catalytic converter efficiency failure
P0441-Evaporative purge flow monitor failure
P0442-Evaporative emission control system leak detected (small leak)
P0443-Evap purge solenoid circuit
P0455-Evaporative emission control system leak detected (gross leak)
P0460-Fuel level unit no change over miles
P0462-Fuel level sending unit voltage too low
P0463-Fuel level sending unit voltage too high
P0500-No vehicle speed sensor signal
P0505-Idle air control motor circuits
P0600-PCM/Serial communication link malfunction
P0601-Internal controller failure
P0622-Generator field not switching properly
P0645-A/C clutch relay circuit
P0711-Transmission fluid temperature sensor, no temperature rise after start
P0712-Transmission fluid temperature sensor voltage too low
P0713-Transmission fluid temperature sensor voltage too high
P0720-Low output speed sensor RPM above 15 MPH
P0740-Torque converter clutch, no RPM drop at lockup
P0743-Torque converter clutch solenoid/trans relay circuits
P0748-Governor pressure solenoid control/trans relay circuits
P0751-Overdrive switch pressed (LO) more than 5 minutes
P0753-Trans 3-4 shift solenoid/trans relay circuits
P0783-3-4 shift solenoid, no RPM drop @ 3-4 shift
P1195-Catalyst monitor slow O2 sensor (Bank no. 1 Sensor no. 1)
P1197-Catalyst monitor slow O2 sensor (Bank no. 1 Sensor no. 2)
P1281-Engine is cold too long
P1282-Fuel pump relay control circuit
P1294-Target idle not reached
P1296-No 5 volts to MAP sensor
P1297-No change in MAP from start to run
P1388-Auto shutdown relay control circuit
P1389-No ASD relay output voltage at PCM
P1391-Intermittent loss of CMP or CKP
P1398-Misfire adaptive numerator at limit or no crank sensor learn
P1486-EVAP leak monitor pinched hose or obstruction found
P1492-Battery temp sensor voltage too high
P1493-Battery temp sensor voltage too low
P1494-Leak detection pump pressure switch or mechanical fault
P1495-Leak detection pump solenoid circuit
P1594-Charging system voltage too high
P1595-Speed control solenoid circuits
P1596-Speed control switch always high
P1597-Speed control switch always low
P1683-Speed control power circuit
P1696-PCM failure EEPROM write denied
P1698-PCM failure EEPROM write denied
P1756-Governor pressure not equal to target @ 15-20 PSI
P1757-Governor pressure above 3 PSI in gear with 0 MPH
P1762-Governor pressure sensor offset volts too low or high
P1763-Governor pressure sensor volts too high
P1764-Governor pressure sensor volts too low
P1765-Trans 12 volts supply relay control circuit
P1899-P/N switch stuck in park or in gear

ENJOY!!

 

did you type all that

 

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Thank you USMCgunrock!

Could one of the Mods please assign this as a Sticky? This is a good reference.

Thanks,
Dan

 

<bump>

Is there a way, other than the "Report Post", to bring this to the attention of one of the Mods?

I still think this would make a good Sticky, for a quick code reference.

Dan

 

Excellent post. Thank you, great reference resource.

 

Hello,
I am new to this forum and forums in general so if I do something stupid please be kind enough to let me know.
Here is my issue. Error code#1594. I have a stock 2001 Jeep Cherokee Ltd. 4.0L, 4wd. bought it new. Started getting the check gauges (battery)(Battery is new) light last Fall (2011) replaced the altern. all was fine until about 3 months later. Ck gauge light came on again. Went back and had a rebuilt computer newly coded installed. The error code is still coming up. All battery cables cleaned and re-seated. All grounds check out fine. no apparent loose wiring. Any one have any comment or help on this. I only have 120,000 miles on this car and would prefer to keep it.
Thanks Folks
Luke199

 

What do you mean by cleaned and re-seated? The terminals? If that's all you did the inside of the cable itself might be corroded. That happened to me (not just on my xj) and as soon as I replaced my battery cables (+&-) it was good to go. I've checked inside the insulated cable and all you see is green tarnish/corrosion. I make my own replacement +&- cables using 2 gauge stereo amp wires with marine terminals (sealed with silicone and heavy duty sealing head shrinks).

 

why is this not a sticky?

 

Here Here!

I do have a question, Code P0138 and P0141 State down stream and pre cat. Seems like is should be one or the other.

 

Luke1999, it could be ANY bad connection from a loose ground to the plug behind the gauge cluster that's setting the code. All that means is the PCM has detected a system voltage that's not right. Usually it's something to do with battery supply voltage but it could be some circuit that sends signals to the PCM like an alternator that's not functioning or something else.

Sometimes you have to interpret the codes yourself. For instance, my WJ 4.0 was showing both a P0442 and P0455 codes and we couldn't find any leaks with a smoke test. A DRBIII scan tool found it. The purge solenoid valve was sticking and causing a variable leak, sometimes big, sometimes small. It was driving me crazy because it was getting close to inspection and we couldn't fix it. In that case the smoke was going into the intake manifold and not showing on the exterior where we could see it.

 

1991 jeep cherokee 4.0 keep pulling codes 75, 73

 

1991 jeep cherokee 4.0 keep pulling codes 75, 73

 

have a P1685 error. Code not listed above

 

https://duckduckgo.com/?q=p1685+code&atb=v191-1&ia=web