Hey guys,

My 99 XJR has had an issue with the drivers side window and sunroof not operating correctly. Drivers side window wont roll down and sunroof will open then close automatically after about 20 seconds. I know of the hard-reset and when I do this it works...for about a week at best. Then it starts all over again. I've ruled out the possibility of it being something simple like a fuse, thinking it is probably the BCM? Hoping for further insight before continuing the investigation...

 

How good is your battery?


These cars are very sensitive to a battery that is not 100%.

 

Just put a new battery in, should have mentioned that above...

 

Anybody have any other suggestions of what may be causing the problem??

 

Just a thought, a lot of times I ask about a battery and people answer they just changed it, well that doesn't make the battery good. So have your battery tested, and make sure you put the right one, with the right CCA rating.

Assuming the battery is ok you have to make sure that nothing is draining it. If your windows work fine after you do the reset procedure that means that somehow the computer is "forgetting" the limits. I have had a couple of cars with a similar problem and ended up changing the module, but before I get that crazy I'll make sure that:

1. your battery is the right battery
2. your battery is good
3. nothing is draining the juice

Then I would move on to something else.

 

Okay, will do. Will keep you guys updated as well. Thanks for the replies guys!

 

I used to have sunroof / window issues too. Then all at once, my XJ8 got harder and harder to start. Changed batteries once, didn't help much. Finally checked the bridge in the positive battery cable at the false firewall - passengers side front. Lift up coating / cable wrap and inspect the wiring. Mine had melted plastic coating it. Checking with a voltmeter on either side of it, there was a sizable voltage drop - enough to cause the starting issue. After cleaning it up, voltage flow was restored again, and sunroof / window issues cleared up too.

 

This is more in line of what I was looking for! Thanks man! Will check battery first but I've almost completely ruled out everything else. Will update you guys when I get enough free time to inspect the wiring...

 

Do a hard reset. Unhook the negative cable at battery. Touch it to the positive. Count to ten and then reconnect it to the negative post.


This clears stored charge from capacitors in all the modules. Sounds too simple but it works.

 

Bumping an older thread here but I this afternoon I purchased a new to me 2000 XJR (in the proper colour, green!). I made sure to roll up and down the windows and the sunroof when test driving the car, and other than the drivers side window being a bit slow to roll up, they all worked fine.
Then literally the first drive tonight after bringing her home the driver's side window wouldn't roll down, and the sun roof would automatically close after a few seconds. Exactly the same problem as OP.

I'm going to try this hard reset tomorrow and see if that solves it. I'll also test the battery at the local auto zone. Someone suggested having an incorrect battery could be the cause, what are the correct amperage specs for the battery?
OP also mentioned the BCM, what is this? Battery control module? That's just a guess, sorry I'm brand new to these cars so I don't yet know all the abbreviations.

My only other electrical gremlin so far is the 12v outlet (cigarette lighter outlet) doesn't seem to work, I was going to take apart the center console and investigate this tomorrow but perhaps this could be caused by the same battery issue?

 

any good working 12v car battery will have enough capacity ( amps) so its not the issue
BMC = Body Control Module
Check the fuse first. nothing to do with battery again

 

When my driver's window will not operate properly, I just perform a HARD RESET (battery disconnect) and the window works normally.

Sometimes the motor fails. Try 'GLOBAL OPEN, GLOBAL CLOSE' to see if it works the motor.

bob

 

Hard reset did the trick! I just wonder how often I'm going to have to keep doing that? All part of the fun, right?

As for the cigarette lighter outlet, it did turn out to just be the fuse. I searched on here and it was suggested the fuse for that was no 11 in the trunk fuse box, label "accessory." That fuse was fine, but I thought a 10A fuse seemed a little small for the 12v outlet, then I found a fuse diagram listing trunk fuse no 5 as "cigarette lighter" checked the fuse and it was in deed blown, one 25A fuse later and it is all working again.
Now onto the next problem, the radio...

 

hard was the answer.

brian sicha

 

These cars are sensitive to minute voltage drops.

Check the archives about how to check ground connections, which is often a contributor.

Also check the archives on how to determine battery age on the calcium battery in your car. Sometimes a prior owner will change the battery for age and just get an AGM or a plain lead acid battery of the same size.

Cleaning the grounds and checking the battery age since the car is new to you will save you some grief.