I am taking my SLK 230 in for the third time to fix whatever the problem is that is causing the check engine light to go on. They are finding a Code P0410 (air injection secondary system malfunction). The last time it was in the mechanic disconnected a switch at the front of the engine that he said controlled the air flow to the front of the catalytic converter and hooked up another one that was mounted there. Apparently there was a spare (in-line) switch. This was ok for a week, then the light came on at startup. Apparently that wasn't the problem. Anyone have any ideas? The engine seems to run fine.