I had a similar problem with the air injection pump. I think it is the same code as yours but mine is on a 500E. The dealer said that the intakes are carbonized and it costs about $ 3K to fix this. It involves removing the head to get to the problem area. For a second opinion, I went to a trustworthy mechanic, He suggested that since the air injection pump only operates a few moments upon cold start up there is not a big concern and he removed the check engine light... This was obviously not a fix but it got ride of the annoying check engine light.

Please keep me posted with your search for the remedy of the air injection fault problem. I will bring all the replies to this post to my mechanic to get his opinion on them.

Thanks and good luck.

Thanh
500E