I have been having the same problem a week after buying the car from Audi so they took it back put new throttle body on as they said it was that still light coming on so then new maf still light coming on then they said they thought it was alternator not giving enough power to sensors so new one of them light went out for a couple of weeks then back on so this time I tried to sort it myself after a bit of digging around the web I found it could be brake light switch so have fitted one two weeks ago and it's now fine .6 pound switch from local spares and Audi under warranty spent well over 1500 in parts