Hi there,
2006 ML500
I have a P0400 code. I cleared the code, no engine light on now, but the code shows when I scan on the merc software of the reader.
It has an option of active testing "y31/1 (egr vacuum transducer)". When the test is run with all the prerequisites, it just makes the idling a bit rough, as it warns prior to test; and that's about it. My question is when you do the test, should the engine stall or run normally. Also why MIL shows no fault. I have driven the car quite a bit since I cleared it. Thanks in advance.

 

Just wait and see if the code returns. If it does, the problem might be the 14 yr. old vacuum hose to the Transducer being cracked.

 

Thanks Major.
The code does exist on the module scan but not on MIL.
Are there 2 of them on this engine? Removal instructions is much appreciated. Thanks

 

No, on a 500 there is only one. If the CEL is not lit, you do not have a problem.

Removing it is very difficult in that it is on the rear of the eng. and you will need a mirror. Don't cry if you damage it.

 

Thanks Major for your help. It just bothers me why I get the code when I do the scan all but no MIL.

 

Does the CEL light come on when you turn the key to pos. #2?

 

yes

 

Then you have nothing to worry about.

 

Thank you