In case it helps anyone with a similar problem. I went to go out in the car (1998 XJ8 4.0). The first symptom was that when using the remote the indicators didn't flash and the interior lights didn't activate. The car started and drove fine for about 20 miles or so with no issues or warning signals on the dash.

After parking up for a couple of hours while I went for a meal, I had the same issue with the indicators and interior lights, but again the car started fine, but this time with the 'check rear bulb' warning light on the dash.

After about 2 miles, the wiper gave a single sweep and all the exterior and dashboard lights went out. They came back on after a second or so, but the same thing happened again, this time out in the country with no street lights - not good. If the indicators were operating when it decided to show the fault, they either doubled in speed or stopped completely until the system came good again.

I checked the battery voltage, which wasn't too brilliant, but not too low either. A new battery didn't cure the problem. My independent mechanic changed the main earth strap from the engine to the chassis and also checked through all the individual earths, the false bulkhead connector and the high current connectors in the boot.

The problem kept recurring at random intervals. It was eventually traced to an intermittent earth fault from the body processor module, which normally goes to earth through the dash metalwork. A separate earth was run from the BPM to the gearbox and the fault is now cured. I was very relieved not to be looking at a new BPM.

 

Hi I am curious if you or your mechanic managed to get a photo of the fix.
I am wondering if the new earth was from the lead plug on the bpm connector or literally from the dash metal to the gearbox metal?

 

A separate ground strap was run from the metal body of the BPM to the gearbox. I didn't see it myself, but my independent Jag mechanic couldn't work it out because there are three metal studs that attach the BPM to the dash metalwork.

All very strange.

 

Strange indeed, maybe the bolts that hold the dashboard metal to the rest of the body metal are corroded and not allowing the earth to transmit correctly.

Thanks for Replying with more detail on where the fix wire went to and from.