X300 IMMOBILISER

[karga]

I've just moved over from ENGINE section in the hope I can get some help with this.
My Jaguar XJ6 3.2 Sport (X300) suddenly had problems starting only occasionally. I would leave it for a short while, walk back to it and it would start. Car ran perfectly until I stopped and then wouldn't start again. Again, after leaving for a short while it would start ok! This got very frustrating as only a few weeks previously she had a new ECU fitted programmed and ran perfectly. Eventually the car decided not to start at all ! That is, no cranking, just silence. My immediate thought was the Crank Position Sensor on the front of the engine, Replaced that but no change. Then I looked at the central gear box shift contact but that is working ok. ( I'd replaced that 3 years ago). I suspected a relay, possibly the fuel pump one in the boot fuse box. That was ok, So I went through all of the relays front and back and inside the fuse boxes in the car checking them with the Multimeter and a 12v battery to ensure the contacts all worked properly. I also checked every single fuse that related to this. I particularly checked the large White Relay Pl1 located behind the front right headlight as I understand is usually the culprit: No corrosion on that : (This car does not have a Inclination sensor, usually located in the left hand side of the boot, so it can't be that): Battery is fairly new and that's showing a good reading. I've even done a Hot Reset, (Disconnected the battery terminals and connected the cables together for half an hour) No change there : I've had a look at the ignition but struggling to see how to remove it. All electrics work fine. Remote locks and unlocks the car ok and the alarm system works as it should do. When i turn on the ignition I note that after a few moments all the lights go out, as they should, but the engine warning light also goes out, and that shouldn't. That tells me that the car is immobilised. I'm running out of ideas now and the car will still not start, completely dead.I hope someone can help me with this immobilisation problem. I've owned the car 21 years now and know every inch of it, but this has got me beat. Any help would be very much appreciated. Roy

[andypryce]

Probably a stupid question, but have you ruled out a duff starter motor?

[karga]

Hi Andy
No it’s not a stupid question :
Because I eventually realised that the Engine warning light was going out immediately after turning on the ignition, all indications are, on information received, that it indicates that the immobiliser has been activated. I assumed that if it was a faulty starter motor the light would have stayed on.
Am I right ? or am I wrong ?
Roy

[karga]

Saying that, just in case, I might as well try the old “tried and tested method”, a good old tap with a hammer, you never know

[andypryce]

Worth a try I think, really not sure about immobiliser and dash lights, hopefully someone wiser will know.

[alec2824]

Some time ago,I changed the headlining in my X300. It would not start and was immobilisedI After many hours I dicovered that I had trapped one of the wires between the headlining and the roof! This gave an electrical short and tripped the immobiliser in some way! Easily fixedI AlecG.

[karga]

Well the Hammer didn’t work I can only think then that I either have a wire shorting out as you indicate somewhere or a bad earth: Going to be a Pain in the a…..

[andypryce]

Hmmm. Can the immobiliser be bypassed, even temporarily? At least you would then know that was the problem. As you say finding a short will be tricky, like trying to find a broken wire in a harness. Might be worth looking for a good local auto electrician.

[karga]

There is a good Auto Electrician in the area, he fitted the new ECU last year. but lead time is about 5 weeks and he’s expensive: I may eventually have no choice. I’ve no idea how to bypass the immobiliser unless someone else reading this knows how. I’ve no problem bypassing it permanently if it gets the car going : Cheers Andy
Roy

[andypryce]

One last thought, have you tried starting it in neutral?

[andypryce]

And also, the immobiliser is part of the security module, located in the boot, I think. You can get a used security module from eBay but that then needs programming to your car, which requires specialist equipment. Not sure where you are, but if anywhere near Nottingham then David Marks is likely to be able to help. Good luck.