In the winter my ABS light would randomly turn on (Disabling ECS as well), then off, reading the forums, it seemed to be a faulty ABS module. In the summer the ABS light became more steady and of course when I took it to Audi it would turn off for that day... Soon after I found I couldn't use cruise control, and after that all the brake lights in the back went out, if it got worse, it would basically not be able to come out of park. The part is $5.00 and the instructions kinda sucked, but once I replaced it, all the above started to work.

Hopefully this helps someone diagnose theirs

 

I had exactly the same issues with the ABS light randomly turning on. The first tiem it happened it freeked me out, I reset it and could notsee anything else wrong with VAG-COM.Eventually took it in to let the warrantee take careof it...

Cheers
Massboykie

 

where are you finding a brake light switch for $5?