View Full Version : Should I replace PCM? Need 2nd & 3rd opinions

08-24-11, 01:51 PM
I posted a thread recently about how the MAP sensor keeps failing every few months on my N* in my 1994 Concours. It does not matter which brand I put in, all crap out the same. This obviously leads me to believe it is something other than the MAP sensor causing the failure.
Edit: Let me reiterate that changing MAP sensor fixes problem for few months. Then the sensor dies after a few months. Replacing completely fixes problem...and the cycle repeats.

Lately, I have been getting P070 codes that seem to be related to random stalls at slow speeds. Cleaned throttle body clean as a whistle, replaced TPS and there is no difference. Code still comes back.

Even more recently, P026 has cropped up and stalls are more frequent and immediately following a stall, difficult to start. Stalls happen even at 40 MPH.

But I can go days without ANY symptoms. Car drives like it should.

I had a mechanic run diagnostic trees on the code. All the wires and TP sensor checked out fine. He didn't want to tell me to replace PCM and be wrong. I have the FSM and for P026, and that pretty much points to replacing PCM since the wires are good.

I am a complete newbie about PCM replacement. I really feel this is what needs to be replaced to fix these problems.

First: Am I wrong?
Second: I don't need the car to last too much longer. Will going cheap on a PCM be a bad idea or should I DEFINITELY go AC Delco?
Third: It seems to me that none of the replacement PCMs come with a PROM. Does this mean I can easily use my existing PROM?

Thanks for helping me. I'm really ignorant on what PCM failure looks like. And lucky enough to have never experienced it before I guess.

08-24-11, 02:19 PM
I may be wrong and if I am, someone will correct me, but I think you can use a junk yard PCM and your prom.

08-24-11, 07:28 PM
Thanks Ranger. After much research, I believe you are right.

Now I'm starting to think that the P070, P026, and a one time P085 code I have gotten, all point to the ISC motor. I think in order to stop the stalls I need a new ISC motor. But this does not help my MAP sensor dilemma :(

I am not near the car right now. Tomorrow I will check operation of the ISC motor and order one of those if need be and continue to keep a healthy supply of MAP sensors layin around :/