www.jec.org.uk

Hi
Hoping for some help please.
The story so far related to my 2003 XJ8 (X350). I can be driving along all well and ‘every light will come on the dash’ including it scrolling through saying all faults are happening. Where in fact the car is fine apart from the aircon and radio do not work. If I stop the car, switch off and restart, it ‘resets’ its self every time. Once or twice it’s dead when I turn the key, but on second go its fine. This can happen every 10 minutes or only every week.
Jobs done so far:
1) Checked and redone the three earth points behind the head lights. Often a common problem.
2) Cleaned and checked the throttle body connections. I read somewhere is this always worth checking.
3) And of course a lovely new battery. Old battery with car switched off was 12.25v, engine running was 14.5v and cold cranking was 10.5v. Old battery was 4.5 years old so time to swop anyway.
The car is still doing its trick of every dash light on.
The help I am hoping for from the electrical expert members is the next job to try. I am thinking of the following:-
1) Check connections to ECU, the thing behind the glove box. The problem sounds global so maybe it’s the plug into the box. Cannot imagine it’s the unit its self as when the car is running Ok it’s all good.
2) Sometimes the drives door will not unlock from the inside handle so something is wrong here. Could this be making the car fault?
3) Sometimes the car says the LH indicator bulb is gone but it’s not.
4) Or ????
Getting to the ECU looks like an awkward job so thoughts from members would be very helpful. Thanks.

Kind Regards Tim

Such a pain these intermittent faults. Any joy with a code reader when the faults appear?

Have you tried a hard reset?

I think that you disconnect both battery cables from the battery and connect them together for half an hour or so.
This realigns the chakras or something.
Make sure that you have the radio code first though.

Thanks Steve and Andy for your replies.

Unfortunately nothing on the obd2 reader. I have even plugged the reader in while it was running with thd fault and found nothing all be it my reader is a low cost one.

The hard reset is interesting. Never done that. I will try it.

Thanks both.

I wonder if there's a problem behind the instrument panel. In earlier Ford-era jaguars, the CAN bus and the other one (whose name I forget) connected at only one point, in the instrument cluster. So for all the lights to come on, there could be an issue there, assuming there's some similarity in the wiring harnesses - that may be an incorrect assumption.

Another thought: all the lights are supposed to come on just after you turn the ignition on, as a bulb check. So perhaps for some reason it thinks the ignition is being switched off intermittently.

Probably neither of those suggestions are much actual use, as they don't give you a way - unless the problem is a loose connector - to see what the fault is.

I'd start with unplugging and re-plugging every ECU connector I could find = with the battery disconnected, of course. They are mostly pretty easy to get at, usually hidden behind carpet or boot liner or so forth; the usual problem is working out how the trim retainers work, and manoeuvring a hand in the correct attitude to release the plug.

Another one to check is for loose or burnt fuses leading to intermittent connections.

Hi Paul

Thanks, some more good ideals. The with help of you guys i now have a list of 'potentails'. Going to have a play tomorrow attacking the list in order of ease of action!

Kind Regards Tim