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Old 11-10-2008, 10:44 PM   #1
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Cool 91 yj check engine light.....

the engine light goes on and off randomly. what do i do to find the code repair it and clear it so it stops appearing? thank you

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Old 11-11-2008, 05:13 AM   #2
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First welcome to the forum.

You can take it to autozone and they might have a scan tool for it. Your jeep is pre 1996 so a standard OBDII scanner won't work so I'm not sure exactly and my FSM isn't very helpful in this situation.

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Old 11-11-2008, 12:33 PM   #3
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I just went through this with my '95. Get a Haynes manual. It has the codes in it.

To see what your error codes are, turn your key from off...to on...off...on...off...on

Your check engine light will flash - sort of like morse code. There will be a series of flashes with short pauses in between flashes, then a long(er) pause, then the second number.

For example, if a code was 23 - you would have two blinks with a short pause in between, then a long(er) pause, then three more flashes with shorter pauses.

The kicker is that after the code(s) are flashed, the computer also flashes 5-5 to indicate it's done giving codes.

To me - the longer pauses aren't much longer than the short ones, and not too easy to decipher.


One thing which may help a little could be to count the total flashes, then subtract the 10 completion flashes, and try to isolate the true code(s) from there.

In my example above - if the code thrown was 23, you'd have 5 flashes for the code, then 10 completion flashes for a total of 15. Subtract the 10, and you have some series of flashes that creates 5 (2-3, 3-2, 4-1, 1-4 etc)
The problem here is that if you are throwing more than one code, it can get ugly.

Anyway - I may be able to help you more...mine was doing something similar. It came on and sometimes shut off. It almost always went off after shutting the jeep off and turning it back on, then it usually came on after a short bit of driving.

I don't remember the code that was thrown - but it may have been 2-3 or 3-2. It seemed to indicate O2 sensor. I replaced it and the light hasn't come on since (last Thurs).

After you make the repair, disconnect the battery for a couple min to clear the codes.

Hope this helps.
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Old 11-22-2008, 04:13 PM   #4
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When your check engine light appears does it seem to run rough all the sudden and then smooth out when the light goes out? if it does its probably a bad O2 sensor. easy fix but it will cost about $50.00
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