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[bill99]

All below is for my 1999 4.0 litre XJ jeep.

So for elimination and test purposes I bought a PCM unit from the US which was listed as a 1999 PCM and I specifically asked if it was form a 1999 Jeep with the immobiliser, which in the US was an optional extra, and the seller said no just a regular 1999 XJ 4.0 litre automatic, so that's fine just what I wanted.

So I expected to disconnect my immobiliser module unit from the steering column well before I connected up and powered on the American PCM and it should run.

Well I did the swap and had the battery off for quite some time during all this and then got everything re-connected and powered up without the immobiliser module, well it would start up the engine for just a few seconds and then cut it out again.  I made a few attempts to keep it running but it was quite clear that the PCM was saying no way.

So apart from being a bit bummed I also noticed that the swapped out unit was still showing the mileage from my old PCM exactly to the mile.

Now this seems to go against everything I thought I knew from the manuals that the mileage was saved in the PCM module, so just to be sure I put the old unit back in and put another few miles on it and then did the complete swap again including the immobiliser module and sure enough the mileage transferred over to the American PCM again and showed on the dash.

Can anyone explain this mileage not changing over to what mileage was showing on the American Jeep that the used PCM came off ?

Also is there something obvious that I have missed as to why it will not run for more than a few seconds, it looks like the immobiliser part of the US PCM software somehow go activated but how when my SKIS immobiliser module was completely disconnected and off the car.

bill

[jay140285]

All I can offer is that I currently have a 1999 XJ in with a buggered PCM and finding a used matching numbers unit is proving impossible!


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[Jonny Jeep]

The cluster and PCM both store the mileage. What is displayed is what's in the cluster.

Does the SKIS lamp illuminate in the dash after trying to start with the US PCM fitted? If it does SKIS is activated.

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[Mike Pavelin]

Yeah, sounds like you got one with anti-theft enabled. Bummer. As JJ says. The mileage is recordedin the PCM, but it doesn't send it to the cluster, which records it's own version.

[bill99]

Thanks for the replies it confirms some of the things I was thinking.

Regards the SKIS lamp it comes on for a second and goes out so that is a bit confusing considering I do not have the SKIS module fitted. That suggests the PCM is not looking for it because it would stay on, so the lamp check is maybe just part of the PCM start-up routine.

At present I have my old original PCM fitted but I will have access to a borrowed professional spec diagnostic unit next weekend and I will put the American PCM back in and see what that says regards SKIS status.

bill

[Jonny Jeep]

Looking in the FSM the SKIM lamp is cluster controlled as it illuminates during the actuator test, so it will self test for a couple of seconds when the ignition is turned on. The fact the light stays out after that with the US PCM would suggest it is none SKIM.

Could it be a fuel issue? have you tried to get it started using starter fluid as a test?

[Brynjaminjones]

Probably not helpful, but are the wires firmly in the new PCM?
My XJ had problems after having the dashboard out because one of the main leads from the PCM through the firewall wasn't connected tightly.

It would start (sometimes) and cut out after three seconds, but the key symbol would disappear from the cluster.

Probably not your problem at all, but might be worth checking.

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