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Reading OBDI 91 and 92 MJ Fault Codes

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Reading Computer Codes

On 1991 to 1995 OBD1 Jeep models you have a way of reading fault codes which can be accessed without a scanner by reading/counting the check engine light flashes. Start by turning the ignition key to the last stop before it starts, ON then OFF three times (do not start) within 5 seconds ending in the ON position on the third time, ( i.e. on, off, on, off then on and stop). The check engine light will start to flash quickly with a small pause in between then a medium pause to indicate the next number in the to digit number and then a long pause before the next set of flashing for the next code. If all is well (no fault codes) you will get a code 55 which would read like this: 5 fast flashes, medium pause then a further 5 flashes. All codes end with the 55 code if you have air conditioning or with a code 33 without and any other codes would have been before it separated by a long pause. The codes will remain after this test so you can cycle through it as many times as it takes to read them correctly. After a problem has been repaired the code will be removed after 50 on off key cycles or if the battery left disconnected over night which will cause a code 12. Here's a video provided by forum member cjomanche showing this procedure. The codes shown are:  12 - 35 - 55

 

 

Code

Description

Probably Cause

11
No crank signal to computer.
Fault in wiring between crankshaft position sensor (CPS) and ECM ( PCM or computer ) or faulty CPS.

12
Battery disconnected.
Battery or power to the ECM disconnected in the last 50 key cycles.

13
MAP Sensor.
No change in Manifold Absolute Pressure (MAP) between engine off and on. Check circuit and MAP sensor.

14
MAP Sensor.
MAP sensor voltage too high or low. Check circuit and sensor.

15
Speed sensor or circuit.
No signal detected from speed sensor. Check circuit and sensor.

17
Engine running too cold.
Wrong or faulty thermostat. Check also sensor and circuit for fault.

21
Oxygen sensor or circuit.
O2 sensor or wiring faulty.

22
Coolant sensor or circuit.
Check temp sensor and wiring.

23
Intake air temp or circuit.
Check air temp sensor and wiring.

24
Throttle Position Sensor (TPS)
Check TPS sensor and wiring.

25
Idle Air Control circuit (IAC)
Check IAC sensor and wiring.

26
Injector circuit resistance.
Peak injector current has not been reached or injector circuits have resistance

27
Fuel injector control circuit.
Will need specialist diagnostics.

31
Evaporative control circuit.
Fault in fuel evaporative control circuit or hoses.

33
Air conditioning clutch relay.
Wiring to A/C clutch fault.

34
Cruise control circuit.
Fault in circuit.

35
Cooling fan relay.
Check relay and circuit.

36
Air switch solenoid circuit.
Air switch solenoid circuit (non-turbo) or the waste gate solenoid on turbocharged models

37
Torque converter clutch.
Needs specialist or dealer diagnostics.

41
Alternator field switch.
Switch not operating correctly and check charging system.

42
Automatic shutdown relay.
Check relay and circuit. Needs specialist or dealer diagnostics.

43
Misfire.
Misfire in one or more cylinders.

44
Battery temperature sensor.
Needs specialist or dealer diagnostics.

46
Battery over voltage.
Check charging system.

47
Battery under voltage.
Check charging system.

51
O2 detects lean mixture.
Check sensor and circuit and for vacuum leaks.

52
O2 detects rich mixture.
Check fuel injection system and sensor.

53
Powertrain Control Module.
PCM (ECM) fault. Needs specialist or dealer diagnostics.

54
Distributor sync pickup.
Change sync sensor in distributor.

55
End of code.
Trouble codes finished or none recorded.

61
BARO solenoid
BARO solenoid failure

62
Emissions reminder.
Emissions maintenance reminder. Needs specialist or dealer diagnostics.

63
Controller failure.
EEPROM write denied. Needs specialist or dealer diagnostics.

64
Flexible fuel sensor.
Flexible fuel (methanol) sensor indicates concentration sensor input more/less than acceptable voltage

65
Manifold tune value.
Manifold tune valve solenoid circuit open or shorted

66
TCM to PCM failure.
No message from the Transmission Control Module (TCM) to the Powertrain Control Module (PCM)

72
Catalytic converter circuit.
Needs specialist or dealer diagnostics.

76
Fuel pump bypass relay circuit.
Needs specialist or dealer diagnostics.

77
Cruise control system.
Check power to cruise control solenoids.

____________________________________________________

From Mopar:

11  No crank reference signal detected during engine cranking. Intermittent loss of either camshaft or crankshaft position sensor.

12  Positive battery input to PCM was disconnected within the last 50 Key-on cycles.

13  No difference recognized between the engine MAP reading and the barometric (atmosphere) pressure reading from start-up.

14  MAP sensor input above or below acceptable voltage. 5 volt output to MAP sensor open.

15  No vehicle speed sensor signal detected during driving load conditions.

17  Engine did not reach operating temperature within acceptable limits

21  Upstream oxygen sensor response slower than minimum required switching frequency.

Upstream oxygen sensor heating element circuit malfunction.

Downstream oxygen sensor heating element circuit malfunction.

Downstream oxygen sensor input voltage maintained above the normal operating range.

Oxygen sensor voltage too low, tested after cold start. (Upstream or Downstream)

Left oxygen sensor input voltage maintained above the normal operating temperature.

22  Engine coolant temperature sensor above or below acceptable voltage.

23  Intake air temperature sensor input above or below acceptable voltage.

24  Throttle position sensor input above or below acceptable voltage. TPS signal does not correlate to MAP sensor.

25  A shorted or open condition detected in one or more of the idle air control motor circuits. Actual idle speed does not equal target idle speed.

27  Injector #1 thru 6, or any combination of individual injectors driver does not respond properly to the control signal.

31  An open or shorted condition detected in the A/C clutch relay circuit. Insufficient or excessive vapor flow detected during fuel evaporation emission system operation.

33  An open or shorted condition detected in the duty cycle purge solenoid circuit. (A/C clutch relay circuit)

34  An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits. Speed control switch input below the minimum acceptable voltage.

37  Relationship between engine speed and vehicle speed indicates no torque converter clutch engagement. An open or shorted condition detected in the torque converter part throttle unlock solenoid control circuit. Incorrect input state detected for the Park/Neutral switch. Auto only.

41  An open or shorted condition in the generator field control circuit.

42  An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.

43  Peak primary circuit current not achieved with maximum dwell time. Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls.)

44  Battery temperature sensor in voltage above or below acceptable range.

46  Battery voltage sense input above target charging voltage during engine operation.

47  Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit.

51  A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

52  A rich air/fuel mixture has been indicated by an abnormally rich correction factor.

53  PCM Internal fault condition detected.

54  No camshaft signal detected during engine cranking.

55  Completion of fault code display on Check Engine lamp.

62  PCM Failure to update service reminder indicator.

63  Unsuccessful attempt to write to an EEPROM location by the PCM.

64  Catalyst efficiency below required level. (Same as code 72)

65  Power steering high pressure seen at high speed. (2.5L only)

72  Catalyst efficiency below required level. (Same as code 64)

77  Malfunction detected with poser feed to speed control servo solenoids.

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Because it's not correct for 91-95 Jeep OBDI. Who knows where that list came from?

 

Oh okay I was just wondering. That's all :thumbsup:

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