I'm having an issue these days with my '06 XJ8 --

Twice this has happened upon initial startup, twice while driving. What happens is every light on the instrument cluster lights up, all the gauges are dead, and every warning bell is dinging, and I get warnings in the message center of every fault the car could have. If I shut it off, it will restart, at least the first time or two. After a few more tries, it won't restart at all. Give it a minute or two, maybe open the trunk (I was going to see if I could disconnect the battery), and eventually it will restart. If I restart it enough times I will get all the lights and warnings to turn off, but then I'll still have the check engine light on.

After a few more drive cycles the check engine light will go off on its own. Scanning it in the meantime however will reveal a litany of errors. Basically what it tells me is that the body control computer has lost communication with the parking brake module, cruise control module, instrument panel, HVAC module, basically every module on the car that doesn't control the engine.

What is happening, and how do I fix this? Is it merely a connection issue on the BCM, and where would I look? Or does the car simply have demons, and I need to consult a priest?

 

This has happened to me only once. My preferred tech found that a few of the 'modules' in the trunk had been knocked loose. We think by the unsecured spare tire.

 

Where are all of these modules located?

 

In the trunk, under the floor, across the back of the car, beside the spare tire.

 

I saw this issue on my '04 XJ8 and it turned out to be a bad battery.

 

What he said. Low voltage wreaks havoc on our Jags.

Replace the battery (especially if it is original), and all should be well.

Take care,

George

 

Battery is pretty new, I replaced it shortly after I got the car last March.

It happened to me again last Thursday. Upon startup I had all the warning lights on, and the parkbrake failure warning and chime. This time I got out and went into the trunk. I kind of fiddled with the connections to the modules in there, as mentioned above; just kind of made sure they were tight. Started it back up and not only were the warnings gone but this time the check engine light was out immediately. Even better, it's been incident-free since. Knocking on wood that the demons have been excised.

 

glad it worked out for you.