Hi All

So i have "P0412 Secondary Air Injection System Switching Valve A - Circuit Malfunction"

I have checked the SAI pump, removed it put 12V it runs perfectly, opened the pump and confirmed no water intrusion and pump spins freely.
I have checked and swapped the relay and the 40amp fuse
I have checked the vacuum solenoid if I put 12V to it it clicks, I have also replaced the solenoid just in case

Code wont go away, if I put my multi meter on the plug that goes to the solenoid should I be seeing 12V at cold start? The weird thing is that even if I clear code after the car is warm which is when the SAI system shouldn't be activated the code still pops up after the 2nd start...

Any ideas would be greatly appreciated been pulling my hair out with this one..

 

another note here, my car has been decatted but has been like that for years now

 

Sorry I don’t know the answer but hope you’ll report the fix when you figure it out. Always good to have this info on the forum since eventually someone else will have the same problem.

 

I think I have a wiring issue here and need to trace where the wire for the sai solenoid and fuel pressure sensor goes.

 

so I am still troubleshooting this issue but its seems to have added more codes now, I am getting a short 2 ground on both the 02 sensors and the intake manifold flap actuator.. I have probed most of the plugs and no short to ground except on the manifold flap actuator plug... does anyone know if one of the pins on that plug is meant to be a ground?

 

ok fixed most of the codes now it was fuse 104, still have the P0412 that code still has me stumped

https://mbworld.org/forums/m-class-w...ror-codes.html

 

so putting 12V directly to the switchover valve you can hear it click (I also bought a spare one) in the car when doing the output test there is no click...

I do have both an open circuit for the fuel pressure sensor P0192 and I am wondering if this is somehow related to the P0412 code for the switchover valve the wiring is in the same harness on that bank... or does anyone know f there is a fuse the fuel pressure sensor and switchover valve?