Djj624

Hello all. I'm new here and I know automobiles pretty well but not really familiar with Audi. Looks like this is the best place for help. Car is a 2004 Audi a6 that I just picked up. Runs and drives great with plenty of power and everything seems great except I noticed some weird things. 1 is that the dome lights work fine when unlocking and opening the door to get in but once the car is running and you click the button to turn the light on it barely lights and is almost like a faint flicker. Also the power door locks will only work if you open the door and hit the lock or unlock button if your in the car while running and doors are shut they won't work along with that the red light next to the door locks flash every couple seconds on and off continuously unless you open the door then they stop blinking(which I'm guessing might have something to do with the door locks not working properly). Any ideas? Maybe a bad ground somewhere?

georgeb944

You will need to scan the car with VCDS for all modules to give you a clue as to the problem.

google "Ross Tech VCDS"

georgeb944

In case you think that you can diagnose this without VCDS, here is the wiring diagram for the central locking module and the interior lights.

Good luck...

Avantly

Have you checked the CEL module under the drivers side footwell carpet for moisture intrusion?

The light flashing on-off sounds like a potential short circuit causing an output to oscillate in and out of over-current mode but it has been a while since I've stared at the schematics. I have, however gotten all manner of bizarre symptoms from CEL water intrusion, from cycling lights to emergency flashers staying on all the time to door electronics totally inoperative including windows.

Djj624

What does the cel module look like and is there any way to test it?

georgeb944

Looks like this... test is to scan with VCDS.

Djj624

It's this interchangable with an 01a6? My son has an 01a6 2.7t. the car with the issue is an 04 a6 s line 2.7t. can I swap for diagnosing purposes?

georgeb944

Sure, give it a try... can't hurt, might help.