So a few years back I sold my 2000 XKR, but I sold it to my brother's girlfriend so it's still in the family. I've since become mechanic on-call for the car (not that I mind, it's my hobby), but it seems to be aging somewhat less than gracefully since it has left my hands. The first issue was a bad headgasket that took some time to diagnose, but finally got it all fixed up and had her back on the road running good for getting close to a year. However, now the car has developed some interesting electrical gremlins that I'm trying to sort out.

The strange part is that it seems like the problems are almost isolated to just one side of the car. It started with the wipers not working anymore. I had them intermittently fail on me in the past, but attributed that to an HID kit I had installed and some possible grounding issues after reading up on the subject. I've since switched her back to the stock halogen lights, but the wipers still fail to work. Additionally, the driver's window memory does not seem to stick very long at all. It will work fine for several openings and closings of the door after resetting, but not the next day. The fuel filler door will also randomly pop open with no provocation apparently. I initially thought this was probably just a low battery issue as these cars seem to be very finicky about batteries, but I took it out and cleaned the terminals up real good and it seems to be carrying good voltage (12.2-12.4). What's more odd is that the passenger side window does not seem to have any issues holding memory. I would think both would be bad if one went as I would imagine they are stored in a common computer.

Does anyone have an idea where I should be looking or any other tests I should run? It's starting to sound more and more like a BCM computer to me, but I'd rather not make her dump that much money on a whim just yet if it's something as simple as a switch. I've read about the door switch potentially causing window issues, but I don't think that's it as the window memory always seems to work after resetting it, it just doesn't seem to stay. I've checked all the fuses and relays for the wipers as well and haven't had any luck.

 

First thing to do is have the battery load tested at your friendly, neighborhood auto parts store or leave the lights on for 20 minutes and then measure the voltage. Less than 12.0v probably means a fresh battery.

Loosing window memory is the first sign of a less than adequate battery.

 

I know I need a battery and on mine it is almost always the pass window that loses mem.

 

I'd go for the simple stuff first.

My intermittent wiper failure was resolved for 6 Euros by replacing the jaguar black 5 pin relay with an off the shelf 5 pin relay.

It would do no harm to invest in a couple of relays and try swapping them for the originals on troublesome circuits. It only takes a minute and is a whole lot cheaper than most of the alternative part replacements.

Just be sure to check the wiring diagram for the relay (from the vehicle wiring diagrams) matches the wiring diagram printed on the side of the relay.

 

12.2 to 12.4 V is not good enough.

 

If the problems are related to one side of the car then I would be checking the ground straps on that side, having first followed the good advice already given.

Jim.

 

I guess the main thing that stuck in my head was that it was only one window that wouldn't keep memory. I would think that kind of information would be stored on a common computer like the BCM and not in each door individually, hence the reason it seemed odd to me that only one window seems to have the problem.

Where would the ground straps be located on the left side? The car does have 140k+ miles, so it could have some loose nuts or corroded joints I suppose.

Also, I did try swapping some relays around in the box with no luck. It was still using old parts, but for instance the headlight relay worked fine for the headlights, but when swapped to the wipers still didn't make them work. I think the issue might just be in the wiper stalk on the column, but I haven't dug into it that far yet. Figured I'd try to get a multimeter on the main column connector to see if I could figure anything out there.

I'll see about a load test this weekend as well maybe. I'm still leaning that way just because so many systems seem to be having issues. It's either that or the BCM in my mind, as I doubt three things would have all failed at pretty much the same time like that.

 

I strongly encourage the battery load test before expending a lot of effort on these problems. The problem comes about during starting when the voltage can briefly dip very low (often well under 9 volts) due to the heavy current drain of the starter on a weak battery. This causes various computers to begin to malfunction.

BTW, the window memory is individually stored in each door module.

 

Okay, been a little while, but had a chance to go over some things. Still have some weird issues with the gas cap randomly opening, but the windows are a little more consistent. Driver's side has started working more often, but still looking into a new battery at some point. Mainly trying to sort out the wipers right now as those are kind of important.

Pulled the wiper motor yesterday and tried to do some digging to figure out what might be wrong. Home/limit switch or whatever you want to call it in the motor was fine and seemed to work correctly. I chased the wires back to their respective relays and those tested out fine with a 9 volt battery (clicked fine and made contact between the associated pins when it was supposed to). Wires seemed to check out fine between said relays and the motor plug, so I'm thinking at this point it must be the column switch. Any other place I should be looking or does this sound right? I hotwired the motor straight to a battery and it turned fine, so it looks like everything is working on that end of the chain. Any advice for checking the wiper stalk on the column?

 

If you were to look at the wiring diagram, you will see that that there is a computer module (the Body Processor Module, BPM) in between the switches and the wiper motor. If the BPM computer malfunctions, as it would from low voltage, the wipers can operate erratically. These cars are heavily computer controlled and not direct wired like many older cars.

This is why, with the loss of window memory clue, there is a direct pointer to a failing battery. Replace the battery first before you waste time trying to hunt down phantom faults.

 

My money is also bet on your battery. In September 2012, my wife's 2006 XK8 began to show the classic sign of a failing battery when her windows would no longer automatically drop that half-inch when the door is opened. That was a telltale sign that I had read about here on the forum. But what I had NEVER read about was the car's fuel filler lid popping open when no one was around. It happened several times, once when I was walking by the car on my way to my truck, and I figured it had to be time for a new battery. So I shopped around, found the best deal, installed a new Bosch battery, and all the signs of a weak battery immediately disappeared and have yet to return....

Like other folks here have already advised you, quit wasting your time on phantom causes and install a new battery. I'm betting that will solve your issues....

 

I keep encouraging my brother to get one as well, just trying to track down whatever I can right now that doesn't cost me anything. Diagnosis is free, so I've been checking everything out that I can along the way. Just got the JTIS, but haven't had the chance to look up the wiper wiring yet. Knowing that it goes through the BCM certainly leads me to believe the fault is in there and interconnected with all the other problems.

 

A side question as I'm an engineer and curious, but if the issue is voltage related, wouldn't it go away when the car is running and has full voltage from the alternator? Currently I believe the wipers don't even function when the car is running, though I'd need to confirm that.

 

I would imagine not because once the various modules(computers) are spooked my guess is they need to reboot which involves switching off and restarting, at which point the low voltage whilst cranking due to a lowish battery starts a whole load of problems yet again. You said in an earlier post you have 12.2/12.4v - that's a tired battery as stated earlier.
First and easiest thing to test )

 

Okay, another update. Put a new battery in several weeks ago and they have been driving it on and off, but the problems still persist. Maybe not quite as frequent, but not really any better. The interesting thing I noted when I was working on it the other day was that the driver's side window appeared to go down whenever the door handle was pulled. I thought it was supposed to trigger off the latch, not the handle. I had the door wide open and whenever you grabbed the handle the window would go down. Does this sound like it could just be a bad microswitch in the latch or some thing different?

The gas door is also still randomly popping from time to time. Most interestingly it happened when I opened the door and sometime when shutting it. Wondering if maybe the wires in the door jamb are broken and shorting?

The wipers are still also dead, so it's either in the stalk on the column or in the body module.

I've also got an intermittent cylinder 7 misfire code from time to time. Swapped coils to see if that was the problem, but am still getting the cylinder 7 code. I know I pinched some wires when I did the head gaskets, but when I pulled all the shielding back and had a closer look nothing looked wrong/smashed. Interestingly enough, when I unplug the coil I get a coil malfunction code, but I don't get that normally, just the misfire. Guessing it could possibly be a bad injector as well, but have tried to test that yet.

Any more ideas where I need to be looking for all these gremlins? The body module is the one that's really staring me in the face, but I'm hesitant to mess with it if there's any way around it. Sounds easy enough to replace from a mechanical standpoint of removal/installation, but programming could be interesting and it's an expensive guess if it doesn't work.

 

This forum saved me a lot of work by letting me know about a low battery affecting the window memory. The other day I came out to the car as it was just starting to rain and found the drivers window down about an inch. When I opened the door the window went down further and did not return when closed. I rolled up the window, drove home and when in the garage I reset the memory up and down and it was working, The next day I retrieved something from the glove compartment and had the same problem with that window so I reset it. A couple of days later I had the same problem and that is when I decided it was time to start checking the forum. It was a big help as I would have never though of a battery problem as the car started fine and I had no other problems. I found the battery had a dead cell (it was still the original factory batter in my 2004 XKR). I replaced the battery and all was fine. I did reset the window controls and expected to have to to the radio and clock but found they were fine. I was also worried as my electronics had not been reset since I installed Mina exhaust and cold air intake and was worried about a possible check engine light coming on and possibly the car running rough for awhile until it readjusted, but to my great pleasure everything went well. The Jag forum has been very beneficial many times in the last two years.