I think I have a wonky PCM?

[robinsone]

So I have 206k on the clock. I was getting some bad gas mileage so I decided to replace the upstream O2 sensor (AC Delco). Soon after I got a P0420 cat code. So I figured it might be a bad downstream O2 since I replaced the upstream. Ordered an AC Delco rear O2. While I was waiting my temp sensor seemingly crapped out (replaced 60k ago with a non-AC Delco). I had no temp reading whatsoever so I went ahead and replaced the temp sensor (AC Delco) along with the temp sensor short sub-harness (AC Delco). The temp sensor and harness fixed that issue.

Replaced the rear O2 and low and behold the cat cod came back. Took it in to the stealer-ship to confirm the cat was bad, they agreed. Got a Walker downpipe from rockauto installed. Cat code went away then I got another CEL. Code was for a rear O2 sensor lol. That disappeared and now today my temp sensor bottom-ed out for no apparent reason. I checked the engine when it was running and both fans were on, not sure if that's a normal response with no temp reading. My thermostat is relatively new AC Delco, and only has about 20k on it.

Not sure what's going on but I'm beginning to think I might have a bad or wonky PCM, I'm guessing the only way to eliminate it would be to throw another PCM in there and see if the issue resolves itself.

Let me know your thoughts I'm at a bit of a loss here...

[Scottydoggs]

you need another new temp sensor, they suck and fail all the time. a lot of the time they are bad new in the box.


the pcm is fine, you'd have bigger issues if it was bad.


and what year car you got and model.

[robinsone]

What brand should I go with then? Or is it just a crapshoot regardless of brand..

[robinsone]

04 gp

[Scottydoggs]

id try to get a delco, or get one from a junk yard, all the aftermarket ones seem to be a crap shoot. 2 and 3 sensors deep till guys get a working one sometimes.

i just did a engine swap not to long ago, i took and reused my old temp sensor just for this reason.