Hello,

Yesterday my wife's 1998 XK8 suffered an electrical failure that has me at a loss.

About a month ago, I was driving the XK8 when I noticed the driver's side sun visor bracket was dangling from the windshield header. I attempted to reseat it on the fly but had no luck. Later that evening, I was unable to shift the XK8 out of park. After a quick search, I found a blown 15 amp fuse in the driver's side fascia fuse panel was the culprit. After replacing the 15 amp fuse, I was able to shift the transmission out of park.

Two days ago I finally got around to taking an in-depth look at the loose sun visor bracket. I found the positive wire to the sun visor bracket had a nick in the insulation. I taped the wire and reinstalled the bracket. I took the car for a spin that night and made multiple stops. All seemed well, problem solved. So I thought.

Yesterday my wife took the XK8 to the grocery store. After loading up her groceries, she experienced the same issues, and she can't shift the XK8 out of park. Rather than talking her through the process to replace the fuse over the phone, I drove to the grocery store to rescue her from the blown fuse.

I pulled the same 15 amp fuse from the driver's fascia fuse panel, and it's blown. I replaced it with another 15 amp fuse. The new fuse blows. Figuring there is still a short in the wire leading to the sun visor bracket, I disengaged the sun visor from the bracket and insert another 15 amp fuse. All appears to be going well now, so I tried to start the car. This is where things went from bad to worse.

As I engaged the starter, the headlights turned on, the horn began to honk, and the wipers began to move. I stopped trying to start the car and turned the key to off. With the key off, the starter remained engaged and continued to crank the engine, the headlights remained on, the horn continued to honk, and the wipers continued to move. I double checked that the wiper switch and light switch were both in the off position.

I removed the key from the ignition, but the starter continued to crank the engine, the headlights remained on, the horn continued to honk, and the wipers continued move. I disconnected the ground cable on the battery and all spontaneous electrical actions ceased. There was a strong smell of burnt plastic coming from the dash/firewall area.

Further troubleshooting revealed another nick in the positive wire providing power to the sun visor bracket. The starter, headlights, wipers, and horn will continue to spontaneously activate if I reconnect the battery. The yellow and red fault lights are illuminated on the dash, the check engine light is illuminated, and there are random failure/fault displays in the gauge cluster info window. I removed and looked inside the ECM. There were no obvious signs of damage or burnt circuits inside the unit.

I'm inclined to remove the ECM and send it to ASI for a diagnostic check. Before I ship it to them, is there anything else I should check? I may buy a scanner and download the fault codes this evening. If I am able to get any fault codes, I will post them.

Any help or suggestions would be appreciated.

Best Regards,

 

Did you try a hard reset? Disconnect the negative battery terminal and touch it to the positive for 15 seconds or so.

 

Yes, I tried a hard reset.

If I connect the battery (and leave the 25 amp started solenoid fuse installed in the engine compartment fuse box) the starter will automatically engage. This happens with no key in the ignition.

 

Just a guess - nothing more, but ............... the "vanity lighting" (including the lighting in the sun visors) is controlled by the Body Processor Module which is behind the dash / fascia.
That's where I would begin looking for charred wiring and/or burned connectors.

 

+1
Both of the two 15A fuses in the LH fascia fusebox feed the Body Processor Module.

If you can smell burnt stuff, then you'd almost certainly have seen some symptoms when you cracked open the ECM if there was a problem in there.

Never does any harm to pull codes, but they might be misleading here.

Mike

P.S. Which fuse was it?

 

I think you might be on to something regarding the Body Processor Module.

This is the BPM from my XK8.



I'll start with replacing this and then see what I've got. Thanks for the suggestions. I'll keep this post updated with my progress.

Best Regards,

 

Note that the BPM is programmable and the proper software must be used at either a dealer or specialist to replace it.

If you are able to find one with exactly the same code, including the digits at the end listed on the VCATS in the trunk, you might get by.

 

That's a bummer. What are the chances I can find a BPM with the code LJB2500AC/063?

If I end up having to get a replacement BPM reprogrammed, would it matter what code is on the replacement unit?


Edit: I think I found the answer to my own question:

If further diagnosis appears to point to a defect within a control module, note the 3 conditions on the following page before interchanging control modules between identical vehicles to confirm diagnosis.

1. Refer to illustration 3, which shows a typical VCATS (Vehicle Configuration And Test
System) label, located behind the spare tire on the trunk floor of XK8 models and behind the
trunk trim on the left side of the spare tire on V8 XJ Series. Each label is specific to each
individual vehicle, and lists the VIN of the vehicle along with the part numbers of the CMs
originally installed in the vehicle during manufacture.

2. In the example above, the part number of the Body Processor Module is identified as:
LJA 2500AG/055.
In the above, the basic part number LJA 2500AG has been programmed during vehicle
manufacture for the specific market and features of the vehicle concerned, and is identified as
/055. This would be the complete part number for a replacement BPM for the vehicle concerned, if it were necessary to order one from Jaguar Parts Operations.
Note that the suffix /055 (in the example above) does not appear on the label on
the CM concerned. This number appears only on the VCATS label of the vehicle.

3. It is permissible to temporarily interchange a CM from another vehicle for testing purposes,
only if:
• The full vehicle history of both vehicles is available.
• The history of both vehicles indicates that the CM in question has not previously been replaced by a CM from another vehicle or by a replacement part.
• The VCATS label information for the full part number of the CM in question on both donor and recipient vehicle is identical, as illustrated above.
• The donor vehicle is known to have no electrical defect.

Thanks for your assistance.

 

Waldo.
I see that you found the 'TSB 418-03am VCATS compatibility' that I uploaded years ago in the large file area. Gus has it on his site also I think.

A BPM from a similar 1998 XK8 Conv. will likely be fine. It would help if a salvage yard would look at the VCATS and confirm the three digit suffix but getting salvage yards to understand and mark all the parts might be asking a little much.

car-part.com will list thousands of salvage yards and they will ship one to you.

I think I am about 40 miles away from you so if you need me to use my WDS to read any modules on the car let me know.

bob

 

98 03 Jaguar X100 XK8 Cuerpo Módulo de Procesador Deportes LJB2500AC 063 | eBay

 

Ah... so close, but already sold. Thanks for the link. After talking with Bob, finding what I need doesn't sound as daunting.

Thank you, Bob. It was good talking with you this afternoon. Your insight was very helpful.

Best Regards,

 

Hi Waldo, did you resolve the BPM issue. I have today suffered the exact same symptoms of erratic electrical happening whilst trying to fix the visor illumination.

 

Apologies for being late with an update. I've been traveling a bit.

Thanks to Bob for pointing me to car-part.com. I was able to find a LJB2500AC BPM from a salvage yard in California. The yard couldn't confirm the three digit suffix, but they could confirm the BPM came from a '98 convertible. That seemed to be close enough, and for $100 was worth a shot.

The replacement BPM seems to have cured the electrical issues. The starter engages only when I want it to. The wipers, horn, and lights are all acting normally. The convertible tops functions as advertised.

I ended up clipping and removing the section of the positive wire that provides electricity to the sun visor bracket. I taped the remaining short section and tucked it up and away from the sun visor bracket. The Mrs is ok without having the lights work on her sun visor if it keeps the electrical demons away.

Many thanks to all for the assistance. It looks like I dodged a bullet.

 

Hi, I have now replaced my BPM, with a used replacement with the same number. Car is now back to its usual self, so I too dodged a bullet! Big lesson learned four me whilst trying to tighten a clip holding the vanity/ sun visor clip!!! Your post really helped me sort the problem tho. Cheers ☺

 

Hey guys! I think I too may be suffering a bpm failure. My 98 xk8 will no longer turn over unless you jump the ignition module (it will not fire but will turn over doing this). However when you insert the key to the car and try to crank it you can hear a clicking noise from where the bpm is located. I’ve replaced the ecm, had the key reprogrammed to the car and a few other things. It is a convertible and how would I go about finding one that is compatible and reprogrammable?

 

Hi Drdude21,
I replaced my bpm a while ago now, it’s easy to do but reading the part number isn’t easy before dismantling glove box etc. But it is doable, by using a torch and mirror up behind glove box you’ll see a white label with a serial number on it. You’ll need this number to search for a replacement. Then it’s a matter of searching eBay, and any Jaguar breakers on line. I got lucky with the number and bought one off eBay. Not too expensive either. Couldn’t believe damage done by vanity light wiring, which isn’t fused and goes straight to bpm unit, in my case burning it out. Hope that helps

 

Hi again just search Jaguar Body Processor Module, there’s loads on eBay. Regards

 

I'd do some more checks before throwing any more parts at it. The BPM only plays a minor role in the engine start. This is taken from the MY2000 wiring diagram but they're essentially the same:



In a normal situation, it will ground the Green/Orange wire to energise the starter relay and signal 'crank' to the ECM, but only if it receives the correct signals from the KTM/ECM and neutral switch.

Try grounding the Green/Orange wire to see if that has the required effect. You may have an issue with the position switches on the transmission or shifter.

Please put the year/model of the car in your sig & profile so we can be more specific.

 

I shall take a look into everything you guys have suggested. I’ll keep you posted!

 

When replacing the BPM, did you have to remove the passenger airbag or just the glovebox and wood panel facial? I think I've got a bad BPM and have the correct replacement.

I'm just doing a couple of other due diligence checks on other areas of the car (XK8) but do have a lot of systems controlled by the BPM going haywire now. Electrical faults have gradually got worse to the point where I'm stuck in park and car won't start with the gauges doing weird things and rattling. Will definitely check sun visor wires again as I replaced the headliner back in 2018. Surely I'd have had problems though pretty much right after that, if these are related to any issue I'm seeing.
Before anyone says it, all grounds have been checked and cleaned, all fuses and relays checked and reseated, brake switch checked and all. Oh and also did multiple battery hard resets. Battery has also been on charge since this I started investigating things 2 days ago (currently disconnected) and has 12.48v which is holding. I've also removed the instrument cluster and checked for solder creep, there is none and the back cover has an 'M' indicating the CAN bus failure was addressed and reworked in the past.