I was driving, and suddenly all of my locks unlock. I get home fine, no engine or tranny issues, seems normal.
Here is what I am experiencing now...
1. I can lock and unlock the car with the key ONLY. Nothing automatic works.
2. Trunk only unlocks with key.
3. Locks do not engage when put in drive, as they did before
4. Unlock button on dash does nothing, as does the trunk unlock button
5. "rear bulb failure" and "trunk open" warning lights and no brake lights
6. I am hearing a distinct "CLICK" when I push the brake pedal / car off. Sounds like it is coming from inside the gearshift.

Does anyone have ANY idea what this could be??
I HAVE CHECKED EVERY FUSE IN THE CAR.

Many thanks to all for any help!!

1998 XJ8 4.0 / 105,000 mi

 

What condition is your battery, have you had it tested?

 

I think it's about 4 years old. I will have it tested, I didn't think of that since everything seemed fine . Thank you very much! I will update tomorrow!

 

Do you happen to know what voltage the battery should test at? I know that the Jags are sensitive about it

 

12.3 volts IIRC.

I put in a Duralast PLATNIUM ($210.00 from AutoZone). It reads at 12.5v. If it's 4 years old, you may consider a new one, especially if the car has sat for any period of time, as when batteries die completely, then get charged up, never seem to quite hold a proper charge anymore. That's what happened on mine, only my battery that was in it was only 2 years old. Also, you may want to load test the alternator. I believe auto AutoZone will do this for free.

 

This is from a post I made yesterday, just an fyi if you let it sit....

+1 avern1....so, if your going to store your vehicle (any make), for a lengthy time of 2 weeks or more, I highly, highly recommend a Battery Tender. It will keep your battery up to par, keeping the ghosts away and making it last longer and knowing it will be ready when you turn that key.
I travel for a living, weeks, sometimes months at a time, so I can guarantee this product personally. I have it on my Jag and a car that is horrid on batteries, my Corvette. Until I recently got rid of it (gave it to Make a Wish), I also had one on my 97 Expedition.
Every vehicle fired up on command every time I turned the key with the Battery Tender. Yeah this sounds like a commercial, but I am speaking from experience of the past 7 yrs.
...btw, I have a Die Hard from Sears in the Jag (7yrs old) and a Duralast from Autozone in the Vette (5yrs old).

 

These have all been great replies and I really thank you all for them!! My jag doesn't sit much, maybe a day or two here and there, but a 4 year old battery may be the issue. I also put a reman alternator in it 2 months ago, maybe not so good. Headed to AZone tomorrow. Will advise after.
Many, many thanks agin to all!!

 

Interesting.. My XJR doesn't lock the doors when I start driving, but everything else works perfectly. Is it possible that one of the previous owners disabled that feature somehow?

 

That JB is an interesting question...I found this and motorcarman answers it..https://www.jaguarforums.com/forum/x...ion-xj8-49155/

 

Ah.. So my guess was correct Can the dealer also disable the turn signal noise? Mine is completely silent, but (again) everything works perfectly.

 

The turn signal noise comes from a little speaker just under your ignition switch that's behind a steering colum cover. I don't believe the early models had the ability to be disabled even from the dealer. Most likely the speaker is no good. Very common.

Next thing I would do to try with your original problem is perform a hard reset. 'Sometimes' wiping out all the voltage to all your modules in the car will be all that it needs. However, seeing as it happened while driving may indicate a possible alternator issue. I'd do what a few posters mentioned about the alternator and battery if a hard reset doesn't help to some extent.

 

It is the alternator! Putting out 12v and battery at 85%. Thank you to all for your help!

 

Okay, charged the battery while waiting on my new alternator to come in and everything seems cleared up with the exception of my remote fob not working.
Is there a reset I need to do for that?
Many thanks to all!