Check Engine Light

[Codytaylor92]

Hello everyone, so i have a 78 CJ7 and the check engine light is on and i don't know how to reset it. its just a custom light to the left of my steering wheel
So i bought this jeep about 3 years ago, i need to get it smog-ed so i need the check engine light OFF!
can i just unplug this thing? i don't see anywhere where i can check the engine anyways, its just a damn light.

please help!

[Desert Dog]

Almost all CJ7s never had a check engine light. People would install one when they upgraded to fuel injection or swapped in a newer engine.

Some California CJ7s had a little "Check Carb" light, a little rectangular light to the left of the steering column, but I thought those were only on the 80s vintage Jeeps. It simply reads a lean or rich fuel mixture on the O2 sensor and nothing else.

the 1978 Model has NO on-board diagnostics for a smog technician to check. If your CJ7 is not actually running a too rich, I would just unplug the damn light, maybe even put a label above it that says "REAR LOCKER" or "OFF-ROAD LIGHTS", lol. They are just going to do a visual and a sniffer on that classic Jeep.

[Codytaylor92]

it has had a engine swap to a 92 yj.
is that going to make any difference?

[Desert Dog]

[quote="Codytaylor92"]it has had a engine swap to a 92 yj.
is that going to make any difference?[/quote]

That will make a HUGE difference, as the 4.0 from a 92 has an ECM with OBD technology. That check engine light should be connected directly to the ECM.

If the engine swap wasn't already approved by a CARB referee, it will be a HUGE headache, as you are required to swap over the entire package, including fuel tank, evap, ECM, air intake, and fuel delivery from the 92. THEN the referee had to inspect and approve the finished product before it can ever smog again.

The 92 motor has OBD1 computer engine monitoring that can be accessed by the smog technician. I had a 91 YJ, and I am pretty sure that the ECM triggers that light when there is a problem with one of the sensors or it is scheduled for maintenance of some kind. Not only will the tech require that the light be out, he may do a light check to verify that it is fully functional.

If I remember correctly, Jeep got in trouble for the early check engine lights on YJs, because they were set to automatically go off after a certain amount of miles of use, even if nothing was wrong, so the dealership could make money servicing it and clearing the code. Jeep / Chrysler has a long history of ripping off customers. So the code just might be for routine maintenance, and might go away after resetting.

[Codytaylor92]

yeah the referee business has already been taken care of a few years back.
ill just have to find where the damn thing is so i can reset it then.
thanks for the help

[Desert Dog]

You can reset the codes with a OBD1 scan tool.

You can also disconnect both battery cables, then touch the ends together for about 10 seconds, then re-connect them. This should reset the ECM.

Then again, If you are having a Real issue, the engine fault will continue until you fix the problem.

[Codytaylor92]

awesome!
thanks for all the help