2009 C6 sedan. Left rear door won't open from either outside nor inside.
Anyone who have tried this before, who knows the best places to cut the inside door trim?

 

Have you scanned the car for modules issues? You may not have to destroy anything, at least not just yet.

 

You can get to the wire harness for the rear door with the front door open, maybe try wiggling it a bit, you probably have a broken/nearly broken wire and the child lock is on.

 

Could be this. Do you hear any sounds when you turn the child lock on and off? Should make a small "klunk" sound each time you lock and unlock the child lock feature.

What about when you press the main door lock button? Can you hear anything inside the rear door?

 

Another thing to do if you have VCDS is see if you can communicate with the door control module. I would bet that it is not communicating. If not, it's likely that one of the CAN wires are broken in the rubber tube between the pillar and the door. With any luck you can pop off the rubber tube on the pillar side and weasel the wires out enough to find the break and stick them back together to get the door unlocked.

 

I get error 02115 Lock unit for central locking-implausible signal.

Also can't operate window from the faculty door, but driver door can operate faulty door window just fine.

So it's a child lock thing.

This is what I can see of the wires:

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Very interesting! I have not seen this failure on a C6 yet. From your symptoms and the code, it really sounds like the electronic actuator in the door latch is actually stuck or something has gone open circuit and you need a new door latch assembly. I've seen this on C5 drivers doors but not at all on C6. So this brings me back to pushing inward on the door with your hand while banging on it near the latch/striker pin with the other, while having someone repeatedly try to cycle the lock from the drivers door button. I believe that is a brushed motor, and my guess is this code can be caused if the brushes go open circuit, or by a failed micro switch that senses the position of the actuator. Maybe you can get lucky with banging on it and get them to momentarily make contact again and turn one last time? Pushing inward on the door a little should take tension off of the latch, I am not sure if that will actually affect the operation of the lock actuator at all, but banging on that area just might help some worn/stuck brushes or micro switches to make contact. Have you tried clearing the code to see if it immediately comes back? If it immediately comes back then it sounds more like a micro switch than a motor issue.

One more thought, are there any special tests for the door module that allow blindly cycling the motors? If the fault is actually caused by a micro switch, maybe there is a way to tell the motors to cycle anyway even though the micro switch is saying not to? I sort of doubt such a test exists in VCDS but might be worth checking.

Here is an interesting thread on a C6 door latch failure:

https://www.audiworld.com/forums/a6-...cking-2879050/

 

A gentle push on the door while operating the key did the trick.


What is this type of screw bit called?

 

That is a triple square you can get them at just about any parts store. I think I got mine at either auto zone or harbor freight

 

IMHO VIM makes the best XZN/Triple square bit sets I've ever used. If you like nice tools, check them out. They are reasonably priced and their quality is top notch for a tool made in the free independent country of Taiwan.