Hi

I'm having a really strange problem with my 1997 XK8 and haven't found any similar problem in forums.

Sometimes when I start the car, put the gearbox on D (or R) and when releasing the brake pedal, the car stalls. It happens only when "rear bulb fail" message is displayed on the screen. The error is very random. Sometimes the bulb failure error goes away after stalling the car few times and the third..sixth time is a success. And there are days when car works perfectly with no problems.

After I get the car moving then it drives perfectly. The initial takeoff is the problem.

Last night I could not get the car moving at all (at least 20..30 attempts).
With the "rear bulb fail" message all the break lights will go on when I turn the ignition on - without touching the brake pedal.

I have already replaced the brake switch for another used one and had no results.
The battery is not fully charged at the moment - but the problem occurred with charged battery also last summer.
The car has newer rear lights fitted and the wiring might be bad.

Sorry for bad english...

 

Yesterday I removed the Security Locking and Control module.
It had no effect on starting the engine but the "rear bulb fail" error remained.

So there was no difference if the module was connected or not.
Can the SLM module be the problem?

 

It seems that the "rear bulb fail" message was totally misleading...

I recharged the battery, replaced the brake switch, cleaned rear light bulbs and contacts. Measured all the wires (also brake switch wires which was totally annoying...) And nothing. The error was still there.

The problem seems to be with the ignition barrel and the rear bulb fail message comes from the security module that can't identify the key (it lights the breaking lights).

If I have the error and turn the ignition in and out few times, then the error dissapears. I can take the key out, put it in and everything is ok. But if I take the key out and wait for 60 seconds, there is a small click sound and after that the "rear bulb fail" message is back again.

Funny thing is that it allowes to start the engine and that's the main reason I could not blame the ignition barrel or the immobilizer. But I don't know yet how to fix the problem. It occurs very randomly. But at least I know that the rear lights are not to blame

 

The problem has not been quite solved yet. At the moment I'm quite sure the troublemaker is third party immobilizer that has gone mad.

I will have this immo removed in Autumn because it requires a quite lot time to spend at the workshop. So it would be wize to to it when the sunny part of the year is over.

At least it works most of the time...

 

Redo the grounds to the rear lights as described in this thread: https://www.jaguarforums.com/forum/x...esolved-35083/

It might just fix your problems, especially if your third party immobilizer is somehow connected to a signal in the taillights.

 

At the very least if you remove the immobiliser you will have ruled that out if the problem still persists.

ECU failures are common on those early cars, so you might want to have that tested while you are at it.

 

Rear light grounding is ok. Already checked that out months ago.
The car has had some serious accident years ago and some really "smart" guys have done new wiring. That's why I couldn't find any similar symtoms from the forum.

Jag + custom wiring is every electricians dream
So sadly standard XK electical solutions don't apply on my car