Originally Posted by Jpnhunter
Thanks I will try that.
Tried the trick got a 12 , 21 , 24 code. 12 is a indicater that the power has been disconnected in the last 50 starts (Offroad lights) 21 O2 sensor, 24 Throttle posioning sensor. Replaced the two sensors and it's running like a top.
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.
Found these codes for my 93 yj jeep.
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:
Code Probable Cause
- 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.
- 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.
- 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.
- 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.
12* Direct battery input to PCM was disconnected within the last 50 key-on cycles.
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