Jeep ZJ PCM/ECU Issue? Please Help!
 

I've got an issue with my 97 ZJ and I am hoping someone out there can help me resolve it.

It started a little while ago...turn the ignition on, the dashboard lights up as per normal, immobilizer de-activated, engine turns over but does not start.....BUT.....a few seconds later, the "check engine" light comes on, fuel guage shows fuel and then it starts.

But...now I don't even get a "check engine" light come on. Fuel Gauge shows empty and not sure if the volts gauge is supposed to show something with the ignition on or not but that is not showing a reading.

Nothing has been done to the wiring, and this bad boy spends most of it's time in the garage. It doesn't do challenging 4wd.

I've read a fair bit on the net and to me it seems to point to the PCM/ECU. I've disconnected it, checked all cables etc but given no-one has been touching this I don't really understand why there would be an issue other than the PCM/ECU itself.

Has anyone else come across this before? In the states it's easy enough to just get a second hand unit to test but it looks like it's going to cost around $400AU to get hold of a reconditioned unit. I've been caught before buying Jeep stuff from the states and not getting as advertised.

If anyone has any suggestions I look forward to hearing from you!

Many thanks.

You are probably correct but I wouldn’t jump to PCM immediately. If your battery is not new, I would try a new battery.

I would also be looking at the fuel pump as mine went a little while back and had some similar(ish) issues as yours.

I put an aftermarket one in and it works again but the fuel gauge stopped working. I found a new oem Bosch unit on Amazon which I will one day get around to fitting. Amazing how poor some of the aftermarket gear is.

Many thanks for your response.

The interesting thing is that I forgot to mention was that trying to use an OBD reader to get codes out of the PCM/ECU yielded no results.

In fact the method of turning the ignition on/off 3 times quickly to get scan codes displayed on the dashboard doesn't work either.

I do know the fuel pump was replaced a little while ago and my jeep has only done 150,000 genuine Km's. I hope it hasn't gone again as it's a huge job.

Thanks again for your assistance

It does seem the ECU is no longer communicating. I think your model vehicle has various reported issues on overseas forums with corroded solder joints on the main board connector interface .

Many thanks for your reply.

Yes, unfortunately I have seen the same articles. Also relates to the Central Display in the dashboard indicating doors open, service, low fluid, etc.

I've even seen a kit off ebay where you open the ECU and replace certain capacitors as apparently that is a thing as well.

Starting to look like I will have to suck it up and try a replacement ECU!