One problem related to check engine light on has been reported for the 2009 Audi A4. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Audi A4 based on all problems reported for the 2009 A4.
August 12, 2017 car was parked in a target parking lot. Went to start and car lights and radio came on but engine wouldn't turn over. Also check engine light became illuminated. Next day car was towed to quad cities Audi to service dept. Audi service dept finally got around to looking at car on Friday sept 1. They state that " found timing to have jumped causing valves to come into contact with pistons and bend. " their repair suggestion states " r&r cylinder head and send to machine shop to determine how many valves need to be replaced. Replace timing chains, guides and tesioner. " quoted $3,729 to fix, plus $595 for diagnosis. Car is currently at that dealership being worked on.