Hello. I am the owner of a Jaguar XJ 3.0d (2015 model,). I am writing to request an official technical assessment to determine whether there was any negligence in the work carried out, following a system failure that occurred immediately after the battery was replaced by an external contractor.



1. Details of the Incident

Date and Location: 6 May 2026, at an external battery supplier.



Work carried out: Replacement of the main and auxiliary batteries (installation of Solite AGM batteries) and battery registration (BMS reset)



Driving conditions: Immediately after the replacement, the vehicle was driven normally for approximately 230 km on the highway. (no warning lights or electrical faults during the journey)



Problem occurrence: Immediately after arriving and stopping, the rear-view camera failed to operate, the door locks jammed, the smart key was not recognised (the message ‘Check key and smart key not found’ appeared) and the power was cut off



2. Current vehicle status (diagnostic results from specialist workshop) When connected to the JLR-specific diagnostic tool (SDD), the vehicle VIN is recognised, but communication with the BCM (Body Control Module / CJB) is impossible; damage to the BCM module is suspected.

Upon disconnecting and reconnecting the main connector of the rear seat fuse box, the vehicle temporarily entered the ACC ON state, but the power to the entire interior was subsequently cut off again. No signs of water ingress or corrosion were found on the BCM connector located under the passenger’s feet.



3. Official Enquiry: We request the technical opinion



Question 1: When replacing the battery in this model, is there a possibility that a lack of connection to the ‘backup power’ or voltage sparks (surge voltage) during the terminal connection process could cause damage to the internal communication chip or hardware of the BCM?



Question 2: Can the fact that the vehicle was driven normally for over three hours on the route (with lights, air conditioning, etc. in use) serve as evidence of the alternator’s normal operation?



Question 3: If an AGM battery from a specific brand (such as Solite) is used instead of a genuine specification battery (such as Varta or Delco), is there a possibility that differences in internal resistance or voltage instability could cause cumulative damage to sensitive modules such as the BCM?



Question 4: If a vehicle that was functioning normally prior to the battery replacement exhibited this communication failure immediately after the first long-distance journey following the replacement, I would appreciate your expert opinion on whether this should be regarded as a typical failure due to the vehicle’s ageing, or as damage caused by an electrical shock during the replacement process.


Thanks
Harold

 

On my opinion your new battery(s):
- Might not have good terminal connection - Check both battery terminals for lose connection. Lose contact can cause that you get some power from battery, but not enough to run all systems correctly. XJ have lot of electronics eating juice out from battery. Same for other direction: You might get some charge from alternator for the battery, but not much to keep up the charge. Poorly made work is quite common human error in a hurry day.
- New battery might be bad. (manufacturing error: internal connections lose etc) This happens sometimes.

Do you have an multimeter to measure current battery voltage?
For good new fully charged AGM battery you should read over 12.6V DC

Can you try to add power from another vehicle or known working charged battery by jumpleads? (connect jumpleads to the main battery terminals)
If you get your vehicle running by jumpleads remove the leads and now measure the voltage from battery terminals. You should have over 14V DC if your alternator is charging.
Measure both: cable terminals and battery. If you get different reading from cable side than battery terminal, you have bad connection between.