So glad I found this forum as I knew an Audi dealership were going to have my eyes out This happened to me (my car is parked up every 3 weeks for 3 weeks due to work) "brake servo restricted" & "start/stop fault" warnings on the dash, and every so often feels like the abs is coming on when braking, found a sensor on ebay £20 it is either a genuine part or a very good copy, watched the YouTube clip and had the job done in 5 mins - warning messages have disappeared so touch wood "alles in ordanung" as the Germans say. Recon I possibly save a few hundred quid, cos you know it would have been an hours labour for finding the fault and another at least for replacing the sensor, and gods knows how much they would have jacked up the pric of the part thanks again.