I've done a lot of research on here, and there never seems to be a solution. Has ANYONE ever fixed this problem on a '94-'95 Z28 with automatic???

This seems to be a particularly devastating error code from my research, causing major issues. Major issues this car had 10 years ago, that I don't want to return (like the 2000 RPM idle!)

I seem to be the first to have this issue come up though... the A/C compressor wouldn't engage whatsoever. When this code was cleared from the ECM, the compressor magically started working again.

How is this error fixed? Speedygonzales on here claims it can be a grounding issue. How do you fix the grounding?

 

I have no facts to back up my theory but cheap optis or should I say when I had a cheap opti on I got that code several times. Has not been back since I installed the delphi. That's my my theory.

 

Your a/c probably started working because the PCM has to be reset after an a/c fault that shuts down the compressor is detected, then fixed.

 

Believe it or not, but this car still has the original OEM opti as far as I know. I suppose I'd have to go through the paperwork to find out otherwise, but I know we haven't had to have it replaced in 10 years or more. If it was replaced, it would have been done while the car was still on warranty and an OEM part.

Interesting, that's what my mechanic said a manual told him, which is why he reset it. I wonder what shut it down? This code 51 has been in the system sporadically for years now, and it has never shut down the compressor before. I would suspect something else shut it down...

 

DTC 51 is EEPROM programming error. The EEPROM is the chip in the PCM. It is not replaceable. From my factory service manual "If DTC 51 sets during normal vehicle operation, replace the PCM." The new PCM will have to be programmed for your car.

You could also try having your current PCM reprogrammed. In one of your other posts you said your car is stock so you could take it to the dealer to have it programmed.

 

I looked up the part # for a new PCM and it's 16188051. Also looked... and there's no way to get a new one anymore. Not many on ebay either.

Even if replacement isn't required, and reprogramming is only necessary, I wonder how much reprogramming would cost from the dealership? I can assume about 3 times as much as it would need to cost.

My Haynes manual recommended quickly tapping on the PCM while the car is running to see if it would stumble or stall. No such problem... so I would assume it isn't a connection problem.

Concerning the A/C compressor issue (talked about elsewhere) that disappeared once the ECM/PCM/whatever was cleared...

I'm going to check the relay for the compressor in the underhood fuse box tomorrow and see if something is up with it. I'll also undo the battery and check the PCM and make sure nothing is slightly disconnected or rattling around.

The cruise control was working fine even while the compressor wasn't working at all, so it definitely isn't related to the fuse that's for both of those.

There's nothing worse than being a perfectionist like me, and not understanding what the heck is going on with something.