Hi everybody -
I'm a newbie who just bought a 2001 XJ8 VDP w/ 75K miles. A wonderful car on the highway, very comfortable. I got it for cheap because it has a few, er, issues. The second is:
The brake/shift interlock is inoperable. When I park the car and remove the ignition key, I get the 10 seconds of beeping. With the key out, I can freely move the shift lever into and out of Park.
Can this be caused by a problem with the Body Control Module (see my other thread) or is it likely to be a mechanical issue with a broken or bent part, or a bad switch in the shifter mechanism? All advice and opinions appreciated!

(BTW, I found and downloaded the famous JTIS files, and compared to what I was used to for my American cars, I was disappointed. In particular, American shop manuals have detailed troubleshooting charts. I haven't found anything comparable for Jaguar as yet. Also, my American shop manuals have clear illustrations of the various wiring harnesses, as installed in the car, so you can see what part of the trim or upholstery you have to uproot to get at them. How do the Jaguar mechanics figure this out? OJT?)

 

The PARK switch is probably broken. The micro-switch is on a plate on the right side of the selector lever assy. It is activated when the lever depresses it in PARK. The sound is that the lever is NOT IN PARK. If you can move the selector lever without the 'key-on, brake pedal depressed' then the the plastic housing is broken or the solenoid is faulty/removed. Almost all the cars that came into the dealer after being in the auctions was that the batteries died and the 'car-lot jockeys' figured that it was easier to 'SNAP THE SELECTOR LEVER LOCKS WITH ONE QUICK MOTION' than to get a battery charger or remove the little T30 TORX screw lock cover. The housings are plastic and I have replaced HUNDREDS of broken housings and bent levers.

You will have to diagnose your own list of faults by disassembly and look for damage!!

bob gauff

 

The answer to answer my own query, after much research:
Someone had completely removed the shift interlock solenoid from the shifter, as well as the "Park" position sensor. The leads for the neutral switch were shorted together as were the leads for the park switch. I replaced the shifter with another one, which had all its parts intact. Now things work as they should (no beeping when engine turned off) except that I have to manually trip the shift interlock to get out of Park - I still have to resolve the short which is keeping the body processor module from supplying B+ to the interlock solenoid. I believe this short is somewhere in the interior lighting wiring above the visors, but we shall see. I plan to cut the interior wiring feed (pin 101 from the BPM) and see if the BPM stops blowing its fuse. If so, that should allow the shift interlock to work electrically.

It's engineering lunacy that so many unrelated functions are all controlled (or disabled!) by the body control module! The shift interlock ought to have a simple key-switched B+ from the ignition switch.

 

Woo hoo! I'm starting to think I might have some automotive troubleshooting talent ....
I did in fact cut the Red/White lead from BPM processor pin 101. Then a fresh fuse in left hand heelboard position #7 did not blow (finally). With that in place, the shift interlock works entirely, as does the tilt/telescope column and the interior "soft" lights. Map lights and visor lights of course do not work. Only surprise was that the outside mirrors still do not adjust. They must be on some other circuit.
I wanted to get the BPM out to see what its part number was, and I have to say that was a chore. I removed the glove box, and found the BPM behind an immovable plate. Somehow, I was expecting it to be more out in the open, or perhaps mounted to the front side of the plate. After unhooking its large electrical connector, I still couldn't get the BPM out, after lots of maneuvering every which way. In the end, I had to unfasten one end of a plastic heater duct, and drop that down. Then I could snake the BPM out the bottom.

 

The usual culprit for the map/visor light fault is the visor mounting fasteners/screws that 'short' the wires to the visor lights. People put the visor back and don't look where the wire harness is routed and just screw the thing in place.

The BPM does not have to be removed to get the part number because you should be looking at the VCATS lable for the last 3 digits (suffix) for compatibility. All the programmed modules are listed on the VCATS lable in the boot!!!!!
The number from the unit itself in not enough info for replacement.

bob gauff

 

Bob -
I had been looking for the VCATS label but I have not located it yet. You say it is in the trunk, er, "boot"? Where exactly -- under one of the carpeted panels? I looked around the perimeter of the lid, and around the battery (have the battery cover panel up), but I don't see it. If it is under a trim panel, which one? Or is it hidden in plain sight?
Also, my BCM is marked LNG2500AB/XXX. Does that mean that any other one marked LNG2500AB/XXX will interchange exactly? Looking on eBay, I see that there are maybe 4 or so different BCM types for sale for XJ8s, including a couple of LNG2500AB/XXX. What happens if you plug in a different type number? Car doesn't run? Other modules catastrophically wiped out? Car is mostly OK but some functionality gets lost?

 

Please read about module compatability before randomly exchanging programmed or configured modules.

bob gauff

 

Thanks for the reference to that document. For a body control module, it looks like if you get one that has the same major numbers (before the slash) it would probably at least mostly work. But it would probably be very scary to swap in an engine control module.
Anyway, my body control module seems to be healthy, so I am NOT expecting to swap mine now! I was trying to understand the engineering and logic behind Jaguar's system. And at least I now know where the VCATS label must be.
This may open a can of worms or a hornet's nest - but have any electronically inclined owners/experimenters figured out how to power up and interrogate a module on the bench?

 

This was the last of these related problems, now fixed. Bob was right, that there was a problem in the visor area. Once I removed the visor, it was clear that the visor lamp wire had been pinched where it goes through the hole in the sheet metal up into the roof cavity. The edge of the sheet metal had cut through the wire insulation, shorting it to the body. With the lamp disconnected, and the red/white power feed line reconnected down at the BCM, everything now works - map lights, glove box light, outside mirrors. Woo hoo ! (with apologies to Homer Simpson)

 

All, I thought I would tag onto Boomers thread in an effort to get some help. My original problem was same.....inop trans shift interlock solonoid, kid broke shifter getting out of park, replaced shifter, found bad #7 fuse in left heelboard fuse block, after reading related threads. Replaced fuse and car ran fine for 4 days. Unfortunately, the fuse blew again. Here's where I'm at: I removed both visors hoping to find a shorted wire. Found nothing, even dropped front of headliner & snaked visor connections out of overhead back to main harness, also removed center overhead console (map lights, etc). I see no evidence of shorted wiring. When I put a new fuse in the the #7 slot it immediately blows. And this is with the key out of the ignition. I'm at a loss for now. I know this fuse services the Body Processor Module, but what wiring system in particular might also be tied to this fuse? Should I start at the battery and trace wires to the fuse block in an effort to find a direct short? Does anyone have any thoughts......?

 

You might do what I did, and cut the red/white lead from BPM pin 101. Be sure to keep each end of the cut wire from shorting to anything else. It is a bit of work to get at the BPM, and drop it down enough to mess with its wiring harness. Anyway, if cutting that wire allows the fuse to be replaced without blowing, you have at least narrowed it down. I forget exactly all that is fed by that wire, but definitely the maplights, interior light, outside rearview mirrors, and gas cap flap motor.

 

Thanks for the input Boomer. After I signed off, the lightbulb in my head went off regarding the possibility of a short between the battery & fuse block. In hindsight, I would presume the short to be after or at the fuse block and not before it. My Son does fold his mirrors in from time to time. Perhaps the wires became chaffed. Also, if I cut the wire, I presume the gas cap defaults to the unlocked position....? Thanks again for your input.

 

Re the gas cap - don't be too sure! When I got my XJ8, little plastic latch inside the gas cap flap was broken off, with the plunger from the latch motor fully extended. Somebody had evidently forced the gas flap open. So after I got the electrics sorted out, I had to buy a new plastic latch. About the only thing on a Jag that is cheap!