2019 Golf electrical weirdness

[RemarkLima]

Hi all,

My neighbour has a 2019 Golf, 2 litre derv DSG.

The story goes like this, there was a sidelight out, so he took it out, tested it and it worked, so put it back. It threw an error, so he disconnected the battery for 30 mins, then reconnected.

Once reconnected, it's gone and throw up loads of faults, the windows will not work, the engine will not start etc... So bricked the whole car.

I have a Foxwell NT530, so downloaded the VW software for it and hooked it up:

The faults are as follows:

02-Auto Trans Control system
Lost Communication with ECM/PCM

03-ABS Brakes Control system
Databus missing message
Databus missing message
Tire Pressure Monitoring System (TPMS) Signal malfunction

09-Cent. Elect. Control system
Databus missing message

19-CAN Gateway Control system
Lost Communication With “Door Control Module A”
Lost Communication With “Door Control Module B”
Lost Communication with ECM/PCM

Etc... Most other modules have Databus errors.

The ECU appears to be next to the battery - could this have been killed? Or is there a CANBUS gateway that's died?

In the Foxwell, there's a whole bunch of options to reset things, or recalibrate etc... But not sure if it's worth trying, or it's a known thing that can be done to get all the modules talking again? Obviously, there's enough CANBUS network to get the diagnostics to work, so must be OK for the most part?

Any help appreciated before it get's shipped off to a menders!

[Quattr04.]

Change the battery, cars can go wild when the voltage is too low.

It may also need coding to the car to work properly which could be the cause of the issues he’s getting now

[RemarkLima]

Thanks - it was my thought, I thought it may have dropped a cell? A multi meter showed 12.5v so on the face of it, it's looking healthy enough.

Do you think if we stuck another battery on with jump leads to boost the voltage this would prove the battery is the issue?

[Belle427]

Cant see it being the battery, id try a disconnect again but only for a minute or so.

[RemarkLima]

OK, so we put the car on a AGM trickle charger overnight and still all the same errors.

Then disconnected the battery for a minute and the same thing. Then attached a fully charged battery with some jump leads just to make sure we've decent voltage and all the same...

So, quizzed him a bit more. A sidelight was out, they took it out, tested it and it was OK so put it back, then checked the fuses under the glovebox - then this is the point it's died. Is there something delicate under the glovebox fuses?

We also tried to re-register the battery with the foxwell, the 70ah, the serial etc... and the same.

Any other ideas!?

[LivLL]

Quiz them again, have they put a jump pack on the wrong way round at some point?

[Belle427]

Have a look around the fusebox area for loose connectors. If they pulled any fuses did they go back in the correct location?

[journeymanpro]

check the earths on the rear light connectors. have seen a similar issue although it was on a polo.

[RemarkLima]

So, long story short - do not disconnect the battery it seems! He got a chap out with the full VAG kit and those modules had lost all their coding, hence not playing with the rest of the car.

Once coded up, all back to normal... What madness! The dipped beam is a wiring fault, which this chap was saying they use really thin wire which just fails, so will need to be repaired.

Anyway, good news they're back on the road! And nothing that we could have done with a Foxwell!