I'm looking for knowledge and experience anyone may have to share about the XJ's computers. I have a '92 4.0, and I'm afraid the issues I'm dealing with are leading me to a bad ECM. I can't get the Jeep to start up, therefore can't retrieve any trouble codes. I've been told that a long string of mutiple codes indicate a faulty ECM, but like I said, I can't retrieve the codes. Power is being sent out to all components when I cycle the key EXCEPT to the fuel pump. I feel I've exhausted all other possibilities. I love this Jeep, but she'll be the death of my patience...

 

I would suggest having a good shop run a test on it,they have the scanners to read the problem and let you know what is going on. That does not mean the dealer is the only one that can help.
Have you checked your cps?
You sound like you have checked everything. Pcms go out but are very dependable.

 

Here's how you can read the codes yourself. The engine doesn't need to run for this procedure.>>->Computer codes

 

Yeah, I replaced the cps two days ago, and nothing. Thanks for the link, I'll research that. My Haynes manual told me I had to fire her up, rev it, turn it off, then cycle the ignition to get the codes. I've only had the Jeep since Aug, so it's a learning experience. Essentially, power is not being sent to the fuel system, and I cannot figure out why. I've replaced everything I can think of.