Our 2000 XJ8 has electrical issues: brake lights, turn signals, tag lights work, as do left front and right rear marker lights. Left rear and right front marker lights and tail lights both sides are out. This problem was intermittent but is now mostly a problem all the time. I have checked the bulbs and the fuses, and have tried to follow all the threads in this forum about similar problems. I am suspecting the BPM.
Can anyone help with:
a how-to on accessing and removing (if necessary) the BPM. It seems to be way up in there; do we have to take the whole dashboard out to get at it? At this time, I want to read the numbers on it, and check the wires coming out of it, before attempting to take it out.
Wiring diagrams; we have the "Workshop Manual" - many thanks - but I can't find any wiring diagrams. Where can they be found?
I may also be suspecting that the battery is not putting out sufficient amperage; it is an old battery, and the weather is cold up here right now. Is this a possibility?
Thanks for your help.

 

If you require a wiring diagram for the whole car then go to this site Jaguar electrical reference and download it for free.

Hope this helps,

 

I got the electrical diagrams, and these are helpful. I am still reluctant to tear into the electrics (side story; I did a little electrical work on my 75 MGB way back when, smelled smoke when I was driving, but everything worked again. Years later I did a little more work; found the wires in the main harness had all melted together; when I separated them nothing worked) without first eliminating some low voltage quirk of the battery, and without knowing whether I will be back at the dealer to reset everything regardless. Any guidance?

 

I see nothing in the wiring diagrams that is common, except the BPM. Personally I suspect individual bulb or connector problems, but I suppose the BPM or it's connector could be an issue.
As for the battery, you can check out the Electrical link in my signature, it's more for charging or starting issues, but it may help.

 

avt007; I checked the link; you're right, it's not directly relevant, but very helpful - done in the kind of way I need to figure things out (better than the old "Chiltons'", like the "VW repairs for Compleat Idiot"). I do have a meter; I was about 12 or a little less without motor, and 13.5 or a little less with motor running - right about the lines you talked of. I am going to look further at the battery before trying to get at the BPM.
Thank you very much.

 

And - oh, yeah - if I disconnect the battery, will I need to go to the dealer for a "reset" when it's reconnected?

 

You won't have to go to the dealer, but will have to reset the radio stations. It will run a little funny and the shifts may be a little rough for the first start, but don't worry.

 

Replace the battery and do a hard reset.

 

The weather finally improved and, after trying a battery charge and hard reset with no change, I took the car to the dealer. They found that a battery voltage issue (my guess is voltage drop in the very cold weather) had scrambled some program of the body processing module, and they re-programmed. I was glad to pay the $150 it cost by that time; it was less than I expected, and saved me tearing out the BPM, buying a new battery, etc.