Hi everyone 🤙
I'm coming with a problem which had become a really nightmare now,
I bought a Jaguar Xf 2012 model and after replacing the start/stop battery I left the service yard and when I got home I noticed that my hazard lights are flashing but I didn't press the hazard button at all that day, anyway I tried to switch them off from the button but nothing happened, also the brake light stays on together with it,
I have to remove the negative from battery overnight so the battery won't get flat , in the morning I reconnected the battery and the hazard lights start flashing as soon as I touched the negative on the battery. ( I have to mention there's no errors on dashboard and the car starts and drive perfectly, also everything else working in order)
I have checked all the fuses and relays possible front and back and also the fuses and relays under the glove box, I have checked all the plugs from all modules and clean them and spray them with contact spray, i also changed the buttons console but still nothing happens, I called the Jaguar center and I explained them my story and they said it might be a BCM failure ....now I'm asking for your help guys if anyone had this problem before ?? Any advice other than I mention will be greatfully appreciated!
in my opinion I try to believe that not the BCM is the problem but who knows ..really weird if so because only hazard lights and stop light stays on, everything else is perfect.

 

I've assumed this was a direct and immediate fault after replacing the battery. Definite cause and effect with no delay between the two events .......

It could be as simple as the security system out of sync and an arm/disarm sequence with the Smartkey will put it right. I do hope you are that lucky.

As you will no doubt be aware, modern Jaguars are very sensitive to battery condition and a partially discharged or failing (primary) battery can give rise to all kinds of weird electrical faults and error messages. With dual battery installations, the most noticeable effect of a failing "starting" (secondary) battery is to disable the Start/Stop function.

The factory procedure for battery replacement on modern Jaguar models (both single and dual battery) includes recalibration of the BCM. Most of us have successfully carried out replacement without doing this although by taking the precaution of ensuring the new battery is FULLY charged BEFORE fitting. Batteries supplied as "charged" are rarely ever fully charged and an overnight charge before installation in the vehicle is advisable.

You could have a fault with the BCM which is on the negative primary battery terminal. It is a reasonable "possible cause" but only a DIAGNOSTICS SESSION session will confirm this. Throwing parts at a Jaguar can soon get very expensive.

There's a lot of components involved in the battery maintenance, charging and monitoring process:

DBM (Dual Battery Module)
DBJB (Dual Battery Junction Box)
GWM (Gateway Module)
Primary battery
Secondary battery

The GWM hosts most of the software required to control the dual battery system and components. It monitors the components and stores fault related DTC's (Diagnostic Trouble Codes). It also controls the charging system software in conjunction with the ECM, RJB and CJB via the high speed and medium speed CAN (Controller Area Network) bus.

The hazard warning indicators are activated by the CJB (Central Junction Box) on receipt of a completed ground path from the hazard warning indicator switch. The CJB outputs a medium speed CAN message to the instrument cluster which operates both the LH and RH turn signal indicators simultaneously. The hazard warning indicators can operate with the ignition switched off, therefore the CAN message from the CJB will also carry a 'wake-up' message for the instrument cluster.

Theory and guesswork can only go so far. A Diagnostics Session is the appropriate first step in logical troubleshooting.

Graham

 

Hi Graham, thanks for your helpful response.
I just dropped the car to a garage who deals with Jag's hopefully they will have time soon and they will look into it because I can't wait to hear they opinion also after Diagnose.
Also how is carried out the procedure you mentioned with arm/disarm sequence with the Smartkey?
Thanks again for replying and I will update here as soon as I have news from the garage 🤞

 

Just lock and arm the vehicle with the smartkey then unlock as normal. If the security system was sensing an intrusion, this should clear it. Worth trying as a component failure at the same time as a secondary battery replacement is some coincidence.

If the garage is going to run diagnostics, they are also likely to try a "hard reset" which puts all adaptions back to default and can often clear strange module behaviour.

Graham

 

As an update, I just got a phone cal from the garage today and have been informed with bad news they said that after diagnose they find out the rear BCM is broken and needs replaced, totall costs will be around €3600 but i think this will go to €4000 because from what they said I need both smartkeys of vehicle and unfortunately one is broken so + 1 smartkey🤯 I really didn't expect that just an BCM could be this expensive
from the topics that I have read in the past I realise that many Jag's owners at some point they have problems with BCM so I think this is a common issue with those cars 😔

 

There is a repair service in the uk.....
https://ibb.co/JjgM3xj

 

Hello ! Have you fixed that problem? If so, did you need to actually replace the BCM or you found another fix ? Mine has the same problem right now, hazards turned on while i was driving, no error no nothing.....