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1991-1995 Jeep Wrangler (YJ) Trouble Codes

Code Probable Cause
11
Ignition
13
Manifold Absolute Pressure (MAP) Sensor Vacuum
14
Manifold Absolute Pressure (MAP) Sensor Electrical
15
Distance sensor or circuit
17
Engine running too cool
21
Oxygen sensor or circuit
22
Coolant temperature sensor or circuit
23
MAT sensor or circuit
24
Throttle Position Sensor (TPS) sensor or circuit
25
Automatic Idle Speed (AIS) circuit
27
Fuel injector control
31
EVAP solenoid or circuit
33
Air conditioning clutch relay
41
Alternator field
42
Automatic shutdown relay
44
Battery temperature sensor
46
Battery over voltage
47
Battery under voltage
51
Oxygen sensor - lean condition
52
Oxygen sensor - rich condition
53
Internal engine controller fault
54
Distributor sync pickup
55
End of Code output
62
Emissions Maintenance Reminder (EMR) mileage accumulator
63
Controller failure EEPROM write denied

The diagnostic trouble codes on all models can be extracted from the Powertrain Control Module (PCM) using a SCAN tool. On 1991 through 1995 models only, the PCM can be placed in the diagnostic mode and the trouble codes flashed on the Check Engine light.

The PCM will illuminate the CHECK ENGINE light on the dash if it recognizes a fault in the system. The light will remain lit until the problem is repaired and the code cleared or the PCM does not detect any malfunction for several consecutive drive cycles.

To extract the diagnostic trouble codes, perform the following steps:
  1. Without starting the engine, turn the ignition key ON, OFF, ON, OFF and ON. The CHECK ENGINE light on the dash will begin to flash.
  2. If any trouble codes are stored in the PCM memory, the CHECK ENGINE light will flash the number of the first digit, pause and flash the number of the second digit. For example, Code 23, air temperature sensor circuit would be indicated by two flashes, pause three flashes. A long pause will appear between individual codes if more than one code is present. Carefully observe the flashes and record the exact code number(s) onto paper.
  3. After the stored codes have been indicated (or if everything in the self diagnosis system is functioning properly), the CHECK ENGINE light will flash a Code 55.
  4. If the ignition key is turned OFF during the code extraction process and possibly turned back ON, the self diagnostic system will automatically invalidate the procedure and must be restarted.

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