I have 2003 A6 3.0 with 56,000 miles. My malfunction indicator light came on last night. After reading the some of the posts here I took my car to Autozone for a diagnostic check and it came back, Secondary Air Supply, Bank One. Can someone please explain if this is serious? Thank you for your help.

 

Probably the best fault code you can get, it won't damage anything to the engine. This system just injects air into the cat converters to heat them up faster in the morning, thats all it does.
Its usually a broken vaccum line to one of the combi valves on the back of the cylinder head.
Look behind the motor and you will see a big silver can looking thing on each cylinder head, those are the combi valves, there is a small vaccum line going to each of them, try to see if one of the vaccum lines are frayed or broken.

 

Thank you for your help.