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):

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 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.
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 fail and must be restarted.
5. 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.
6. 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.
7. 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.