This may be a bit long winded but I want to give some history and details that may have some clues for the more experienced experts here.

About 4 years ago I inherited a 1996 Vanden Plas when my mother passed on. I brought the car back to Georgia from Florida and replaced the battery and tires, and drove the car occasionally (1-2 times per month). I've only had a few minor issues with the car, replaced a coil and the sparkplug tube seals, fixed the AC due to a Schraeder valve leak. About a year ago we had the car stripped and repainted.

About a year ago I noticed that the battery was running down prematurely if I didn't start it every couple of days. I believe the security system backup battery needs to be replaced. I replaced the car battery and bought a battery charger/maintainer and disconnected the battery.

Last November I had a medical issue and the car sat (on charge) until March. I took her out for a drive, and noticed the Ammeter dropping. I took it to O'Reilly's and verified the alternator was bad.

As of yesterday I finally have gotten strong enough to wrench on vehicles again and I replaced the alternator, the car fired right up, and I took it for a "victory lap" to get some lunch.

Here are some odd things I noticed yesterday when getting the car up and running.

• After I got the car put back together I fired up the engine. let it run for 5 or so minutes, and shut it down to re-tension the belts. I noticed an odd popping sound from front passenger side of the vehicle, maybe behind the passenger headlight.
• The door locks were sluggish with the FOB and even the dash switch was intermittently locking/unlocking the doors. I replaced the FOB batteries
• At first the trunk would not open pushing the logo, only the key. But after a few times of cycling the system the electronic lock would work. PROGRESS

HERE IS WHERE IT GETS WEIRD...

• After coming back home after lunch, the car sat for a couple hours.
• I aired up the tires, and was planning on taking the wife out for a drive/dinner.
• I noticed that the security/marker light (small bulb in outer headlights) was flashing every 10 or so seconds. I have seen this is the past when I tried to lock the car and a door or trunk was ajar.
• I cycled the system a couple times and then it went haywire-
  • All of the locks started fluttering including the fuel door. Not that the locks were opening/closing but you could hear and feel a rapid tapping like the solenoids were trying to activate.
  • Then the car went half dead.
    • Car will not start.
    • FOB or dash switch will not work.
    • Headlights don't work other than the marker/security light
    • Moon roof opens but dome lights and trunk lights don't work.
    • Turn signals won't work but Hazards will ???????
    • Cooling fans come on even though the car is cold???

This is what I have tried so far-

• Disconnect battery let sit for 30 minutes, reconnect. No luck
• Pulled and checked all of the fuses in the boot/trunk. OK
• Attempt reboot of Security module via the battery cables, no difference.
• Attempted FOB relearn (Key position 2, Valet switch cycle 5 times) no luck.
• On odd thing is that when I reattach the battery, I hear a slight pop/noise from that sounds like a half hearted attempt by the chirper. Similar to what I heard when I was re-tensioning the belts.

Thoughts/suggestions on next troubleshooting items?

 

Cooling fans on low with key in pos 2 is normal, assuming the car has the TSB mod or was produced after that change in production. So I'd eliminate that as a symptom of anything wrong.
Have you checked the battery voltage? Then, assuming that is good, performed a load test on it?
I'm not sure if the security beeper has an internal battery, but if it does, that may be the reason for the occasional, seemingly unprovoked chirp. I have a hangar-queen that started chirping like that from the right front corner. Also rigged with a battery minder. It's been awhile, so memory foggy, but I believe I disconnected the battery from the car which had no effect (this is the cloudy part). What I'm sure of, is I disconnected a connector in the right front to make it stop, as I was working a PAS fluid leak at the radiator attachment right there and it was annoying. Come to think of it, now that I've mended a few majors on that car such that I can move it in and out of the shop as necessary (It's still a long way from road-worthy) I should reconnect that junction. Will come back here and post a pic of the offending party when I get a chance..but that is likely 2 weeks or more out. The important point is that the car started just fine after sitting, undisturbed for over 6 months. I also mended the windscreen washer bottle in that span....foggy memory again...but pretty sure that connector I unplugged is still adrift, though there is some small chance I re-connected it in the process of re-fitting the bottle. Haven't restored the front bumper/fascia yet, so I doubt it.

 

Aholbro1,
Thank you for the reply, particularly about the position 2 fans coming on. I didn't remember the fans coming on in the past, probably just didn't notice since the car was quiet and the doors closed.

Security system battery. I must have read something for a different model a year or so ago. I've done a search on this forum and a Google search and I cannot find any info on a "backup battery" for a X300. Sorry for the confusion.

Battery strength- since the battery is less than a year old and the car fired right up multiple times on Tuesday I don't think this is an issue, but I may yank it to have a load test anyways. BTW voltage is 12.8v.

Other symptoms I'm seeing.

• Shifter is locked and I don't hear the solenoid when I depress the brake.
• One odd thing I forgot to report in the original post. When I used the key in the door I could unlock the car, but not lock the car. Only the FOB would do this.

 

I don't know what your issue is, but here are a couple of suggestions for investigation.

1. Battery Voltage - You should test the battery voltage as various points on the car. Even though you may have strong battery, there are a number of connections for the power to get from the battery to the fuse boxes and hence the components. You can check the power distribution in the Electrical Guide which can be downloaded from the "How To" section. The primary candidates for problems are the 3 bulk head connections. You can follow the thick cable from the LH/RH Engine bay fuse boxes back to the bulkhead to find these. The Centre connection is for the Starter/Alternator.

2. BPM - Some (many) of your symptoms are with functions controlled by/interfaced with the BPM (Body Processor Module). I produced a spreadsheet some time ago with a list of the inputs/outputs to the BPM. It may be worth using that as a checklist of what is/isn't working and see if there is a correlation.
https://www.jaguarforums.com/forum/x...m-pins-211770/

It's unusual for the BPM to stop working completely. The normal failure mode is for some functions to stop working but who knows. The BPM is easy to access to check connections.



My money would be on a voltage drop somewhere along the power distribution circuit.

 

Brendan,
Thank you for pointing me in a direction to investigate. I downloaded many of the Tech files the other day, your spreadsheet is now part of my toolbox

I'm glad you confirmed a suspicion I had, which was that something was going on with a body control module since the odd random items that are not working.

Cheers!

 

Experiencing odd issues post-battery replacement is not uncommon. Check for voltage issues, and inspect the security module and antenna. Cold solder problems are possible. When considering a used replacement security module, ensure it's compatible and in good condition. On a different note, have you explored securitylicensetraining? It's valuable for enhancing knowledge in security matters, even beyond automotive concerns.

 

Hard Reset by taking both battery cable once removed from battery and connecting them together ?

The longer the better like overnight , you can use battery jumper cables to clamp together and place a shop towel over the battery post

If it were a non - USA model there would be a precaution on the stereo head locking out / theft [rotection

Your power distribution to the important components ( BPM and SLCM ) is from fuse 3 and 4 of the trump fuse box ( hot at all times and no relay required to close )

But the power source wires pass through the large BT4 connector above the fuel tank , fwd trunk panel needs to be removed

This connector should have a tie wrap on it to hold the lock over bar engaged for best pin contact

If you remove it it can be tricky to reconnect it least break the external pins for the lock over bar

There are a couple layers of sheet metal cutout that the edges can prevent you from easily re engaging