Klaus has given you what I think is great advice. I would only add that ECMs (engine control modules and computers) fail VERY rarely, especially on European cars, unless the car's electrical system has been subjected to extreme high voltage abuse (like a lightning strike or maybe disconnecting battery while car is running). Almost all failures that may seem ECM related are due to loose, corroded or worn out external connnections, sensors, or switches. My most trusted mechanic says he has replaced maybe one or two ECMs in his entire career. This above all indicts your dealer.