YJ codes

Need to know why that Check Engine light on the dash is glowing? The light will remain lit until the problem is corrected and the code is cleared. The codes below give an indication of the type of failure(s) and can be extracted using a SCAN tool.

However, by doing an ignition key dance, you can place your 91-95 YJ into its diagnostics mode and extract the trouble code(s) from the PCM via flashes of the Check Engine light.

Perform the following steps to extract the code(s):

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 51, Oxygen sensor - lean condition would be indicated by five flashes, pause, and one flash. A long pause will appear between individual codes if more than one code is present. Carefully observe the flashes and record the code.
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 fail and must be restarted.
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 51, Oxygen sensor - lean condition would be indicated by five flashes, pause, and one flash. A long pause will appear between individual codes if more than one code is present. Carefully observe the flashes and record the code.
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 fail and must be restarted.

Code	Code Name
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

Codes taken from service manuals.