I have several codes reading out but dont know what each code is for. The codes are 18, 31, 43, and 56. Can anyone let me know what these codes are for? Any help would be wonderful. Thanks

Here'* a list of the codes. https://www.gmforum.com/specifications-general-information-132/obd1-codes-retrieval-gm-1983-95-cars-trucks-%2A%2A-278820/

Thank you so very much and thanks for the fast response. One more question. I was looking at the codes and 56 said quad-driver mudule #2 circuit. What does that mean exactly?

It'* a device the PCM talks to that turns on other devices. I saw a few references to cam sensor, one knock sensor and a crank sensor. I suspect these are all controlled by the same quad driver. Does the engine run?

Yes but runs like some crap. It seems like once the engine warms up is when it starts running like crap.

Sounds like a bad cam or crank sensor.

Where exactly is the quad driver module located? I apreciate all your help on this issue.

Not sure where that is. Billboost may have a better handle on this.

Who is that?

He'* our top gearhead here. He might be on tonight, or tomorrow morning.