jclift

Alright Jeepers, I'm having no luck when it comes to finding a good PCM / ECM / ECU. When I bought my 99 Cherokee some of the gauges didn't work and after a lot of trouble shooting I found out the problem was in the PCM.

So I bought a used 97-99 model PCM from a standard transmission 4.0 Cherokee like mine. What I didn't know is the PCM I bought was out of a Jeep with California emissions and my Jeep was built to federal emissions standards. So a check engine light comes on for emissions equipment my Jeep never had.

So I bought another PCM from a 97-99 model and with this one the oil pressure gauge doesn't read correctly. When you turn the key on it goes to about the first bar on the gauge and doesn't change after the engine starts. Just stays there like it's not getting a signal.

I recently just bought another used PCM from a 97 manual transmission, 4.0 cherokee, hooked it up and the same thing is happening as the last one, the oil pressure gauge sits at the same point and doesn't move and the fuel gauge seems to be reacting poorly.

To ensure something wasn't wrong with the oil pressure circuit I hooked up the first PCM I purchased and all of the gauges work flawlessly.

Is it possible that the pinout on the different PCM's changed for the oil pressure gauge and two of them I have are sending the wrong signal to the oil pressure gauge? Or did I just luck out and get three PCM's that wont work for my Jeep?

Thanks for any help and sorry for the long explanation.