My 09 C63 has been throwing the engine light and code on and off several times. The stealership just gives me the runaround saying I can drive the car with the engine light on (even tho it may mask another issue) and that is just not good enough for me. I cold started it this morning and the secondary air pump runs for around 30-45 seconds and then shuts off. I looked at the fuse/relays under the hood next to the fire wall but I have no idea which relay is for the secondary air pump. The fuse diagram in the trunk doesn't appear to identify the relays. Is it possible to have a bad relay throwing the code even tho the air pump comes on in cold start conditions? Could someone tell me which relay is the secondary pump relay if you are looking at the fuse panel from the front of the car and is there a fuse that also goes with the relay. I know from researching the issue that this is a common problem but it is so annoying staring at the darn engine symbol every day. Thanks for all help.

 

Yes it could be a bad fuse/realy causing the CEL to pop up. But IMO your pump shouldn't run if the fuse or relay is faulty.
As for which fuse is it I cannot tell you which one unfortunately.
But i don't understand MB is not able to tell you where the fault is?

 

If your airpump runs than it's not a relay or fuse for the air pump. So knowing where it is, isn't important. Im very confused on all of this. So you payed the dealership to diagnose your car and they told you to just drive it around with the cel on and it doesnt matter? Or you took your car to autozone or where ever to get the code read and then went to the dealership to ask them whats wrong? Most mb shops dont use generic obd codes. There's not really a common failure on m156 secondary air injection. Clearly not the relay or fuse in your case. so you've got the pump itself, hose from the pump to valves, the valves, vacuum lines to the valves and switch over valve, switch over valve, tubes from valves to heads, heads, possible electrical/wiring. If you are expecting the dealer to just diagnose your car for free based on the code which is what it sounds like sure they'll give you a run-around answer. codes dont tell you what part to replace in most cases.

 

The long story is the car is still under CPO warranty. When the code first threw back in October I took the car to Plaza Motors in St. Louis a Mercedes dealer. The service manager told me the following story when I was notified the car was done. He said check engine light was PO410 secondary air injection system. Now when he told me this story I had no idea what a secondary injection system was or its parts. He then said a sensor was registering slow and that a replacement part would have to be ordered from Germany but the service technician just so happened to have a used one his his toolbox and put it on and cleared the code so hopefully all was well. I left with the car the engine light was off and everything seemed fine. Within two weeks the light was back on so I took it to a different Mercedes dealer closer to my house. After watching the mechanic on closed circuit tv run computer diagnostics they backed the car out and the service manager at the second dealership stated that it was the same code but everything checked out ok so they cleared the code. He said my car was a "race car" and things like this happen with race cars. He said it was ok to drive around and it wouldn't hurt the car. Otherwise, if the light came back on he would have to contact a regional service representative and they would need to hold the car for a few weeks to get it figured out. After this retarded conversation I reviewed my first work order from Plaza Motors and there was no mention of a bad part or that a used part was put on so I suspect they did nothing and just cleared the code just like the second dealership. I have since spent hours reviewing the secondary air injection system and the various parts and the various fixes. The car is still under warranty so I want the issue fixed but now you see the runaround I have been getting.

 

i have the same car and the same code comes up. but my pump doesnt work on a cold start. i took some of the top hoses of and its fairly clean inside. where would the fuses be located and the relays?

 

https://mbworld.org/forums/c-class-w...e-again-2.html

https://mbworld.org/forums/c-class-w...ir-pump-2.html

check out my threads on this, its already happened twice to me.

If i was you id replace the fuse and relay first, open up the pump blow it out with an air gun. see how long that lasts if it happens again then go on and take the valves off.

one issue i found was the relay and fuse was popping up somehow, if yours aren't clicking in then you need to mess what that first. Its a pretty easy job.

 

I finally found the problem with my 410 code! I had fixed all the vacuum lines in front to the check valves etc. Still got the code. Cleaned the ports under the check valves and still had the problem.
Swapped out check valves and air pump as I conveniently have a second 1999 E320 but that was not the problem either. Then I gave up... Several months later I went to replace the valve cover
gaskets and discovered another broken vacuum line at the very back of the engine that I had not seen. This line comes out of the firewall and into the middle of the intake at the top. Fixed that line
and the code has not come back!