Recently my wife's 2006 A4 2.0T Quattro had the check engine light come on. Ran the code and it was for P0011. The car ran fine and always has. Light comes on and off sporadically. Sometimes its on for days, then off for days, but always runs fine. Went through inspection last week. The car failed for 2 codes P0011 and P2181. I googled both codes and still not sure what to do. Any help would be great. Timing belt was done 2 years ago just fyi

 

P2181 is probably your thermostat. It's possible it could be the coolant temp sensor and that's something you can try first (as it's cheaper and less labor), but most of the time this seems to turn into the t-stat. Does it come up to temp slowly or wander around the gauge? It should come up to midway on the gauge quickly and stick there steadily. If it doesn't, it's another good sign your thermostat is stuck/bad.

No clue on P0011.

 

It seems like the temp gauge gets around halfway and stays steady, but I've seen it more on the cold side as well. Maybe I'll have the t-stat changed and hope that clears that up