Electrics - one fault after the other (central locking, reversing camera, electric sliding door)

[Jbjorling]

Haven’t read the codes yet, but starting thread to sort of store my thoughts.

Bought my T6 Multivan 2016 in June this year. At first everything worked without a flaw.

First thing to act up was central locking. Wouldn’t work from driver door button. Locks with fob, but no deadlock, and pressing lock on fob once more (to release deadlock and deactivate sensors) does nothing. Scanner reveals passenger and both sliding doors to have ”implausible signal” or something like that.

About a week later right hand side electric sliding door stopped working. Opened fine, but didn’t react to button presses to close. Once manually closed it only released the lock on keypress, but no sliding action of the door.

Thought I’d take a look at it once I got back home, started the car and put it in reverse and the recersing camera has a distorted flickering picture and then it went out - Parkpilot not available.

Once I got home reverse is working again, but with a grainy picture… sort of like interference, and the sliding door started working again after manually opening it and pushing it open.

I believe all this routes through the BCM (called control supply unit in the service manual… I think).

So I’m thinking
1. Poor battery (either main or secondary battery… don’t know if I have a secondary)
2. Some common connection/junction that these things share has poor connection for some reason
3. The BCM (control supply unit?) is faulty

Either that or 3 door modules have simultaneously gone bad, and then both reversing camera and something controlling the right hand side sliding door at the same time.

Another interesting thing; the door sometimes work, and when it does the camera does as well but is grainy.

If the door acts up, then the reversing camera does aswell. And if the reversing camera acts up I know the door won’t work either.

 

[Dellmassive]

Have you had a conversion?

Or seat swivels?

The wire loom runs under the passenger seat, up the B pillar, then along the roof shoulder and down the D pillar.

So trapped cables, drilled wires, loose plugs, corrosion on wet plugs are all possible issues.

Post some pics so we can see what's going on.

 

[Dellmassive]

The electric side slider control unit can also suffer from water ingress and corrosion.

 

[Jbjorling]

Thanks for the input @Dellmassive. I'll post some pics when I get access to a camera (the one in my phone has stopped working).

Made some headway regarding issue no. 1 - central locking. I believe I have isolated one fault.
Implausible signal was previously from passenger and the two sliding doors. Cleared all fault codes, and error is still present. I.e. using the button on the driver's door the doors lock and unlock immediately after. Although now it complains on the driver's door having an implausible signal. The passenger and the two sliding doors are all of a sudden not implausible.

Viewed live data and I think the "implausibility" comes from the fact that the driver's door is indicated to be locked and in safe mode, when it's not. If I open the door just a bit the door module indicates that the door is open, but it's also still locked and in safe mode - that sounds implausible to me.

If I open the door even more the "locked safe" status dissapears and it's indicated as "unlocked" just like the other doors. So that's probably just a frayed/broken wire in the loom between driver door and chassi.

Unless that frayed wire somehow interfere with the right sliding door control mechanism and all the other door modules I probably have more faults to find.

Main battery seems fine - around 13.5V when engine is on, and even after having drained it a bit using all sliding doors and running the fan only on ignition it seems to never go under 12.6V. When starting the car it dips to around 12.4V. Haven't found a secondary battery yet - if there is one is that located under the passenger seat? If so, I don't think I have one. Checked the cables under the passenger seat but just on a visual inspection they look fine. I half suspected I would find a connection loose so I could just pop that in place.

 

[Jbjorling]

Realized I didn’t answer the questions in your previous answer.

It’s not a conversion van. It’s a T6 Multivan Highline from the start and the front seats do not swivel as far as I know… although, I wouldn’t be displeased if I found a lever that allows them to.

Everything looks neat, clean and undrilled so far, but I’m still gonna look more into the connections under the passenger seat first and then dig out wiring diagrams for all the faults and start with the overlapping points such as junctions and cable routing.

But before that - dig into the loom between driver door and chassi.

 

[Jbjorling]

Don’t want to jinx anything but everything is as it’s supposed to be at the moment (for now).

Haven’t really fixed anything so there is some underlying problem, but without the symptoms it’s hard to diagnose.

Hopefully it stays this way indefinetely.

 

[Jbjorling]

To sum up this thread, since most issues have been solved as far as I can see.

The central locking and reversing camera issue was probably related.

The central locking was due to two faults; 1. wiring harness in driver door (wear and tear) and 2. tailgate latch sensor.

Squeezing the driver door harness and wiggling it fixed the issue temporarily, and that also fixed the reversing camera. Best guess is that it introduced some type of signal distortion.

Then the automatic open/close for the tailgate stopper working, which after some troubleshooting led to the latch sensor.

I still haven’t switched out parts, but the latch has been cleaned and the wiring harness has been temporarily fixed.