On my ML350 got code 410 (secondary air injection) Which scared me because on mySL500 M119 I had to pull the heads for it.......
On the 06 ML I tested the air pump.Its good quiet good air flow.
Tested the changeover valve its good vacum and electrical
Tested both air valves at the heads they open and close and hold vacum.
Tested both heads with compressed air and cigar smoke so ports in heads are good, smoke and air come out both sides.(thank God!)
I know there is a relay that ops the system it opens the change over valve and turns on the pump. Does any one know where it is and how to test it? ,and can there be any other causes for this to malfunction??
Star finder does not show any pictures of the relay or its exact location in the eng compartment fuse relay box can I swap it with another one some relays look the same. Thanx in advance John............................................

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88 W124 3.0
96 R129 119eng
06 ML350
98 ML320 sold
02 CLK55 amg