Occasionally while driving, almost every warning light on my 2011 XJL Supercharged's dashboard illuminates.
Here is a Video.

This is followed by the car telling me faults with multiple different systems in the car, (Gearbox fault, suspension fault, e-diff fault, etc.), though there isn't a pattern to which specific systems fail, and sometimes some systems will still continue to work.

Sometimes, the engine temp indicator, fuel gauge, and speedometer also all fail and drop to 0.

I do hear the low battery chime / beep occasionally, and occasionally the car tells me there is a "Charging System Fault".

Oddly, when this situation does occur, the battery voltage seems fine at around ~12.7v-13.0v. As far as I can tell, the car doesn't think the battery charge ever drops below 75%. As the battery voltage doesn't drop below this, I'd assume the alternator is functioning okay.

Also, the car runs perfectly fine and smoothly even while all lights are lit. There are never any engine related fault codes, and every essential part of the car seems fine (headlights, indicators, etc.).

I have had the AGM battery replaced in the car at a generic discount workshop, and recalibrated the BMS afterwards, but the issue still remains.

Almost every module in the car generates a fault code relating to lost communication. The only other fault code I've found is "U00001-88", relating to a CAN bus fault.

Any thoughts as to where I should begin troubleshooting?

 

Ground connections. Then battery positive ones.

(Do not over-tighten.)

 

I had the same issue on my 2012 X351, took it to the jag dealership, $ 3700 later with a new alternator and battery everything has been fine, gpk