I must be one of those unlucky people to experience one of the "mysterious electrical problems" with my Jag.
The other day we had very serious rainy weather conditions. I ran through a couple rather deep puddles, and everything started from there on.
First, the locking "beep" would act as if key was still in ignition - it would screech instead of beeping. That went away after the car sat in the garage for a day. Next day, however, I drove on the highway about 20 miles and stopped for a bite to eat. Suddenly, as I parked and the car was still running, the entire dash board lit up like a Christmas tree. It flashed several times and left the "service airbag" message on it. I let car sit for about 30 min, then started it again and in 5 minutes or so the dash board started acting crazy again.
I decided to drive my BMW for a few days and let the car sit for over a week, thinking that it needs to just dry out. Took it out for a 10-mile highway run, and everything was fine. Stopped at the gas station, put gas in, inserted the key in the ignition to start - and woot! very brief flash of all lights on the dash board, plus the doors locked almost immediately. I drove home for two minutes and parked - no issues. Decided to let the car sit now, until I receive e-bayed used BCM I bought for $30, which I'm planning to swap and see if that makes any difference.
Hopefully someone will come along with some solid advice but if they don't.......
Unless there's signs of water in the cabin or trunk I'd focus on underhood components, especially those low enough to get doused with road water.
I've had no opportunity to dig into an X300 electrical system (knock wood) so I can't tell what to check specifically but I'd just start unplugging electrical connectors and relays looking for water intrusion. Check the grounds a "+" junction posts, too.
Pacific Northwest USA
1988 Ser III VDP V12
While you are unplugging and plugging the connectors, you may as well give them a shot of water dispersant. WD-40 is sold for this purpose, but there are other products that may be better. Dielectric tuneup grease is also good for the wire entry ports on the connectors.
As mentioned by Doug, the ground points are worth looking at. Probably, worth looking at first because so many systems are involved together.
So, you don't think that just letting the car sit for a while might resolve the issue? After a long day of work last thing on my mind is digging under a 4,000 lbs vehicle... the thrill is long gone . lol
Well, nothing was found after "opening some panels" and checking visible connections. I was told to now seek dealer help; however, I'm going to try to detect a faulty ignition coil first - have two new ones, just didn't have the time to work on it. Thanks for checking back.
A really good place to check first is a pair of 18-20 way connectors right behind the RH headlights, next to the washer fill neck. One white and one black. Corrosion and mung likes to set in there, and a good splash of water can do them in. Take 'em apart and clean them up, and see if it helps any.
Well, Jack has saved the day! I popped open the hood, opened the ignition coil cover to expose 6 coils, and tada! One of them was flickering. A newly replaced one I must add. Quick (less than 5 min) replacement job I had done all by myself - and the car runs like new. Thank you Jack! Here's his post from the other thread:
Originally Posted by JackJ
Just for kicks, try this. It must be done at night so that you can turn the surrounding lights off once the car is running.
1. Raise the hood.
2. Remove the coil cover, that's the plastic part that says Jaguar.
3. Turn off all the lights and see if there is a visible flash at the top end of any of your coils. THERE SHOULD NOT BE.
If you see a flash it is a discharge that is causing your ignition system to die out. Whichever coil/coils is/are flashing need to be replaced.