'99 C280 check engine light on but machine runs perfectly. AZ guy says it's the secondary air injection system. What should I expect? Any help would be greatly appreciated.

 

There are a couple of possibilities and it can be difficult for the novice. I have had thed vacuum switchover valves fail more than anything. I have also had quite a few of the air inj diaphragms and motors fail. It is a pretty simple diagnosis for the experienced tech but can be difficult for a novice.

 

Thank you sir. I'd rate myself very much a novice.