fault code P0471

[Brian Martin]

Hi , I was wondering if any body could me with a bit of advice please.
I have a c220 cdi 2005 coupe . I used a obd scanner on my car and its coming up with the code P0471 but only at tick over (780 rpm ). If I raise the tick over by 100 rpm it doesn't come back until the engine is at idle. If I take the car for a good hard drive it doesn't come back till I re-start the car once I have stopped it and restarted it. The car isn't going into limp mode ,but I do notice a lack of midrange power if I don't clear the fault.
I have changed the dpf sensor, cleaned the cat and dpf. disconnected the upstream and downstream pipes and its still doing the same thing .
Oh when the pipes are disconnected the fault still clears when the engine is running above idle .

 

[ChrisA]

Exhaust pressure sensor

 

[Brian Martin]

Thanks for your help Chris I will get another sensor tomorrow

 

[BlackC55]

What dpf sensor did you replace?

 

[Brian Martin]

I replaced the dpf sensor on the back of the airbox. Replaced the exhaust back pressure sensor today, but still has the same fault.

 

[Brian Martin]

Just a thought, if the egr valve was not quite seated properly could this cause the problem even if its not showing any fault codes with the egr valve ?

 

[gurjd]

Hi
Brian, I know this is a old thread and sorry to bring it back up again, but I am recently having the same sort of issues with the same car, I have a 2005 c220 cdi coupe, getting the p0471 code on the obd, when ever I clear it comes back after a short time and restarting the car, did you manage to fix the issue, if so please can you help advising me how or anyone that can help much appreciate any advice thanks.