Last week, my wife was driving the Concorde when the check engine light came on. I checked the codes and found a P0601 check sum error. The car was running fine at that time, just the CEL was on.

Based on research, I decided to replace the PCM and ordered a remanufacured unit from Auto Computer Exchange.

When I got the reman PCM, I installed it and let the car idle. The CEL was off and all seemed well. After about 5 minutes of idling, the CEL came back on and the car started to run really rough, the RPMs were bouncing all over the place, and the exhaust smelled horrible. I pulled the P0601 code again.

I called Auto Computer Exchange and they are sending another PCM out to me. Since I needed the car, I re-installed my old PCM. I started the car up, the CEL was off and the car ran great. I was going to let it idle for 30 minutes just to make sure all was good. At about 25 minutes, the CEL came back on, the car ran rough, RPMs bouncing, and the bad exhaust smell came back. The code showed a P0601 again.

This morning, I started the car, the CEL was on and it ran smooth. I let it idle for 5 minutes, it stumbled once during the 5 minutes but never again. The CEl was still on with the P0601 code.

No other codes are showing.

My question is, does it sound like my PCM is really bad, or are there other things possibly going on?

Any help would be greatly appreciated.

Thanks,
Ed

 

Just to see what would happen, this morning, I disconnected the original PCM, then disconnected the battery. I let the car sit for about 10 minutes. I then hooked the battery back up, then the PCM.

I started the car and let it run for a few minutes. The CEL did not come on and the vehicle ran just fine, though the exhaust did smell a little. I did not have time to let it idle for a long period of time to see what would happen.

 

the pcm still needs to be replaced to start