I put it on the computer and the trouble shooting code was po411. the definition stated that the secondary air injection system fault. explanation: the air injection system is monitored for fault. problem cause:
1. circuit relay defective or fuse open
2. check connector and wiring
3. air pump defective or hoses block

Where would I start to trouble shoot this problem?

Well we need more information . Model, year, engine, etc....

Try searching and if you cant find anything try posting in the corresponding forum

I have a '99 VW Passat, and I had that same error message. I kept clearing it, but it came back. It might mean that the hose is pinched--if you are lucky. I actually took my car to the dealer last week to have them fix it, and it ended up being the pump. Cost me $700 to fix---$400 for labor. Ittook care of the problem though--it was really annoying me. Hopefully you won't have that same issue. If it's just the hose, it should cost you around $300. Hope you have the less costly issue. Here is a link I found that shows you the problem. It's for VW, but I'm thinking it should be the same for the Audi:

http://forums.fourtitude.com/zerothread?id=1995162&page=1

Hopefully this helps..