Hey all, 2015 Jaguar XF Supercharged 5.0.

A couple months ago, I came out after a couple errands to a not starting car. Ignition would turn on, but no crank, and there was several warning lights on the dash. I reset the battery hoping it would fix it, instead, it put the car into the "smart key not found" state. I then had it towed. After several weeks, a local mechanic managed to get it running, but it now had permanent E Diff and Adaptive Dynamic faults, and after a few days, the blinkers and windshield washer spray started to be inconsistent, especially for the first few minutes after start. Also, especially after sitting, the car would freak out on start with countless warning lights. Letting the car idle for 30ish seconds and then restarting would clear these. Sometimes the car would throw lights and not crank, but it would start eventually with enough messing around with the start button and brake pedal.

I started to suspect that the local mechanic had improperly repaired the BCM and corrupted the EEPROM. I obtained SDD v168 and a genuine Mongoose cable. In the process of trying to hook up a battery support unit, I inadvertently damaged the negative clamp, reset the battery again, and put the car back into a no start state. I got a new negative clamp (with the BMS module integrated), and ordered a new, preprogrammed BCM from Mugglestone Engineering and fitted this, as well as a new Duracell AGM battery (in doing so I noticed that the old battery was the traditional flooded type). Running immobilization in SDD did not get the car out of its no start state. As I'm still quite the amateur when it comes to SDD, I then had Tech_JLR remote into my system and he managed to get the car running again. This time the E Diff and Adaptive Dynamic Faults were gone. However, there was now a red "battery not charging" light on the dash (BMS was reset for the main battery). 13.7 volts at the battery with the engine running, this went up under load. Fault codes were B13C5-92 and B11DB-87 from the GWM, and U0447-00 from the PCM. I drove the car normally after that, monitoring voltages at start and running, didn't see any weird values. Voltages varied from 13.6 to 14.6 with the engine running. At one point I drove a 7 hour round trip without issue.

I then ordered an Exide EK151 - the car has been without an aux battery for over a year and a half. Fitted this, and B13C5-92 and U0447-00 went away, B11DB-87 stayed. Stop start is also now reporting as available (it was not before), but the car is yet to shut itself off.

And now for additional complications - I washed the car a couple days ago, and then a couple hours later started it. Once again, countless warning lights on the dash. Let the engine run for a bit, restarted, lights gone. A couple days later, drove in the rain, and after a couple stops, chaos on start again. Blinkers did not work during this either (hazards were fine). Restarted, and this time the E Diff and Adaptive Dynamic lights stayed on. Got the car home, cleared codes, didn't come back. At this point, I was suspecting water ingress - I took apart the trunk, inspected every wire I could find, didn't see a thing. I also had my girlfriend pour a cup of water on the rear glass while I was in the trunk, and didn't see a thing. I did the same test for the front windshield while I was looking near the front BCM - again, nothing. And now, the car will sometimes not start initially. Like before, enough tries and waiting around with start button seems to eventually start. And for more fun, B1D36-15 from the IPC is now persisting through DTC clears.

I found a post on the XK forums talking about how connecting a battery support unit directly to the negative ground could damage the BMS, especially on 5.0s. I did exactly this. I have unplugged the BMS, and as far as I could tell, the car's behavior did not change.

And finally, the last bit of info I have - I attempted to run the "Power Supply Service Mode Diagnostic" as recommended by SDD, and was unable, as SDD kept telling me to unplug the battery support unit, even though there was no battery support unit attached. I also tried to run datalogger, and got "tabman error = error."

I know this is a long post, but I am at a loss as and severely miss this car working properly. I have already ordered another negative clamp/BMS sensor assembly, as they are not too expensive. But I am unsure if it will fix everything. Any advice would be greatly appreciated it.

 

Do you have 2 keys

 

Yes, I do

 

Update: Couple days ago the car started smoking after cycling the ignition (which failed to clear the codes this time). Smoke was light, white, and from the driver side under the hood. Engine sounded and looked fine. Close to the strut tower, I could smell something sharp (not like coolant or oil). Planning to jack it up and take the wheel off this weekend to get a closer look at where the smell seemed to originate. Thinking (and hoping) that whatever electrical fault I have has now degraded to the point of heating up enough to smoke.

Any thoughts or advice before I take a closer look?

 

Maybe a chafed cable shorting to ground (body/metal part). Odd if so as normally a fuse would blow.

 

Following.
This is an interesting one.

 

Update. Got driver wheel and arch liner off, poked around. Found that water drains directly into the pictured area, which seems like bad design, but I’m not sure if it’s really the cause of the issue.
Tomorrow I’m gonna look for the engine ground strap and check its condition. Any ideas where exactly it is? I haven’t been able to find a solid answer anywhere.

 

Try the Electrical Guide etc (& workshop manual if available) for that and much more.

 

Conclusion, in case somebody else has similar issues.
A lot of running around with a lot of different mechanics, but what it finally turned out to be was an intermittently bad resistor in the instrument cluster. Got it sent somewhere for repair, problems fixed. No idea what caused it, if anything.
The battery not charging light was unrelated, and replacing the BMS fixed it.