I have a 1998 Jag XJ8L. After starting the engine, the gear shift interlock won't disengage and I head clicking behind the dash. Related failures at same time were: Manual steering wheel adjuster doesn't work. Automatic adjustment (upon starting and via 3 presets) does work. After manual/emergency disengaging of interlock, steering wheel adjusts slightly/repeatedly while driving. Solenoid clicking behind dash can be heard during these "adjustments" but not like the first time [which was continuous]. Now, when parked and engine is running, if I press power window switches at end of cycle I hear the clicking and the steering wheel "adjusts" slightly. Any suggestions? Thanks.

 

Check your battery. A weak battery can cause all sorts of crazy behavour. Also put the car through a full reboot. i.e. Disconnect the positive terminal on the battery for a few seconds. Touch the positive battery cable to the negative post on the battery for a quick second, then reattach the positive cable back on the battery. You will have to reset all memory presets, but may clear the other crazy problems.

 

Thanks. I was going to try to unhook the battery tonight to reset the computer, but I didn't know about grounding the unhooked positive battery cable for a second. I'll check the voltage first and then try the reboot. I'll let you know the results and thanks again.

 

Well, I tried the reboot by unhooking and reconnecting the battery. It didn't work. The interlock won't release, the seat/steering wheel presets work, the manual wheel adjustment doesn't work. AlsoI noted the map lights don't work and if I put a turn signal on while the car is running the steering wheel "adjusts" slightly up and/or down with every click of the turn signal. I'm guessing the body processor module is on the fritz. Any other suggestions on how to run this down? Thanks.

 

Well, I didn't get a lot of interest on my little problem, but I did manage to get it fixed and provide this info for those of you who may be interested. As the thread indicates, I was starting to think the Body Processor Module was fried. But, before I spent $900 for a new or $200 for a used one, I noted that that little computer is fed by no fewer than four 15amp fuses. I started pulling them and, you guessed it, I replaced a bad one and everything's working fine. In retrospect I now realize that the interlock, map lights and manual steering wheel adjust were all out, which is the description of that one fuse (servos, motors & lamps). But the confusion came with the fact the three seat/wheel presets all worked (voltage from another sourse apparently) and the circuit bleed over which made thesteering wheel"adjust" with the turn signals. Anyway,that's how I fixed it with a $0.35 fuse.

 

Good to hear you got it fixed. I`ll have to keep that tid bit info in my data banks!!

 

We're all glad you found the problem. More importantly, it really appreciated when someone does as you did and post the findings and what it took to fix it.

 

rahiggins, I know this is an old post, but I wanted to say your experience saved my tail! My Son had broken numerous plastic pieces of gear shift assembly trying to get car out of park. Once I replaced assembly, obviously I still had the same problem. Did a search and came across your thread. Same symptoms. Imagine that.....anyhow, got out the electrical manual and started looking at fuses. Found one blown, replaced, all's good for now. Your write up was excellent, and led to a quick fix of my own problems. Thanks!
Ralph

 

There's a 'moral' to this story:--
Before condemning ANY microprocessor based controller, checkout its power supply arrangement! In this case a dodgy fuse, but ANY dodgy connexion anywhere in the +12volt supply OR ITS GROUNDING ARRANGEMENTS could be responsible.
In my experience with micros., at least half the problems are to do with the power supply. Problems internal to the micro. are often due to things as simple as corrosion due to water ingress, very subtle dry joints*, and electrolytic capacitors that have "gone off". Other problems are often to do with simple plugs and sockets getting invisible corrosion and altering pulse timing so it's out of sync. with the clock. If your plugs/sockets live in hostile surroundings, check 'em! Usually, plugging and unplugging a few times will make it work if that be the problem.
Leedsman.
*To see these type of joints, you need powerful magnification and very bright lighting. As most chips are soldered by solder paste and infrared heat in a machine, one sometimes gets a little row of bad/partially soldered joints on a chip which don't show up until the thing is in service. Repair consists of applying a tiny amount of paste flux to the suspect joints and soldering them with an iron containing a bit which has been filed down to resemble a freshly sharpened pencil. There I go, giving trade secrets away! I don't care if it helps someone.

 

I have these exact same symptoms and found a popped fuse. The fuses for the body processor module are in the rear seat footwell fuse boxes. There are some on both sides.