My 2001 XJ8 has sat with battery disconnected for a few months. Went to crank it today and got GEARBOX ERROR and INCORRECT PART FITTED, although no parts have changed since it last ran.

I do have a failing body control module - the only thing affected to date is headlights not operating - if that could be the source of the error codes if it has failed further?

Also noting that engine is reported in failsafe mode - perhaps that's why car won't start?

I'm lost as to what happened since I last disconnected the battery - it ran fine then! Advice?

THANKS
Howard

 

The boot was actually open when I filmed this, so that part of the error message is correct.

But everything else just appeared - the last time I started it about three months ago. No issues with starting then. Won't start now. Battery freshly charged (but at its sell-by date).

 

Install a good charged battery, and also connect a battery maintainer (not a charger to the car), positive lead to the battery and negative lead to the chassis not to negative on battery. If you don't have a battery maintainer than use another running vehicle with jumper cables....
Than connect a scanner and see what codes you have, IDS/SDD will be best if you have that, if not use another autel/launch/icarsoft etc....

And yes it could be your BCM that is causing the issue, diagnose it and make sure.
or just replace the BCM and see what happens

 

When you see engine trans and abs at the same time CAN is down.

Try to communicate with the ECM it uses K to pull codes.

 

There was a post on here recently, by motorman I think (ex Jag tech guy, writes lots of great technical info), that mentioned if some modules are unpowered for too long the capacitors in them go flat & cause this. I think he said he had to reprogramme them to the car to solve it.

 

Capacitors can diy of power, that's not an issue with any jag or any vehicle...
Whats important is when all modules turn on, if there isnt sufficient volts and amperage to power all the modules correctly, than what happens is the info on the eeproms and microprocessors gets corrupted... modules/computers need to have the correct volts/amperage to operate and read and command each other correctly...
And this is a known issue with JLR BMW VAG VEHICLES.
Think of it as if you are using an oscilloscope, if your power is not sufficient that means your reference single is not accurate, which means what ever reading you are getting is not correct either.
computers need to have correct power to be able read and write their eeproms and microprocessors, when power is low, than thats where the corrupted info happens...

SO JUST REMEMBER CORRECT POWER IS REALLY IMPORTANT...
!!! AND DO NOT EVER USE A CHARGER ON A VEHICLE, ALWAYS USE A MAINTANER !!!

 

@hstovall1, use a voltmeter to determine available voltage across the battery terminals with the ignition in the OFF position. There needs to be a minimum of 12.6 volts for the vehicle modules to function correctly. Use a code reader to determine if there are any DTCs stored as they may indicate a place to start with a diagnosis once the correct voltage is available.

As mentioned in the posts above, use a maintainer to keep the battery charged. Don't disconnect the battery as the emissions monitors then need to be reset, and other modules may not function correctly after being reconnected. The PCM and TCM communicate across the CAN network; any missing or faulty signals between the modules may cause the TCM to place the gearbox in 'limp mode'.

Since the vehicle has been left unused for several months, check the engine compartment wiring looms for any signs of damage from rodents chewing on the wires, or water collected in the boot.

 

I might try a hard reset and see what effect it has.

 

I've found the post that I was thinking of, it disagrees with you.

https://www.jaguarforums.com/forum/n...eply&p=2642854

As he's seen it several times it's worth baring in mind as a possible issue.