W204 C250 CDI fault code P0472 only with cold engine

[Slaurro]

Hi there!

I had some problems with my 2009 C250 CDI. The DPF was clogged so i went to a tuning company and had it removed.

The problem is i`m still getting P0471: Exhaust Pressure Sensor Range/Performance. I used to get it before i removed the DPF as well.

I get the fault code only in the morning. First drive seems ok, but if i stop the engine before it gets warm and start it again after a couple of minutes the car goes into limp mode. I have an ODB, i scan the code... P0471.

If i don't stop the car until the engine gets to optimum temperature (about 15 minutes), there are no problems, it doesn't get into limp mode if i stop and start it again.

My catalytic converter is still on the car... Is there any chance that it is clogged resulting in a high pressure on the exhaust? If so, wouldn't the car show any other symptoms? And would it only cause problems when cold? Is there any way i can test and see if my cat is clogged?

Apart from that, i can't see why i would get P0471... maybe the sensor itself is faulty. Does anyone know the part number for the sensor or where it is located? I googled around and i found two types of sensors: exhaust pressure sensor and differential pressure sensor. Are they the same? If not, which one do i need?

Thanks alot!

 

[Slaurro]

I`m beginning to think that the problem is the sensor itself. Does anyone know where the back pressure is positioned in a w204 OM651.911 engine? I wanna take it out and try cleaning it...

 

[Slaurro]

Sooo... i cleaned the Exhaust Back Pressure sensor. But the problem didn't go away. I think i`m gonna order a new sensor and see if that helps.

Before i do that, i will also clean the EGR. I saw that the sensor is mounted directly on the EGR...

Could a clogged EGR cause Exhaust Back Pressure faults when the engine is cold?

 

[boyt]

Who done the dpf delete? Sounds like they haven't done the ecu side correctly?

Regards andy

 

[boyt]

Ignore last comment, yes sounds like it could be a faulty sensor, does your scanner do actual values/live data

Andy

 

[Slaurro]

When they did the DPF delete they removed the differential pressure sensor. They said it was enough for this type of car. Anyway, i was getting P0471 before i did the DPF delete so i don't think it's related.

I cleaned the sensor but the problem didn't go away. It only triggers the fault code after the first start of the car, in the morning.

I`m going on Monday to have the EGR cleaned casuse the EBP sensor is mounted on it... although i think another fault code should have popped up if there was a problem with the EGR...

What else could plug the exhaust apart from the cat?

 

[boyt]

The sensor is mounted just on a elbow that runs the exhaust gases to your egr valve, the valve is mounted lower down, and the vacuum cell.you can see by the ebp sensor is for the egr cooler bypass. I would go with a new sensor. Where abouts are you. I probably got a few in my box you could try.

Andy

 

[Slaurro]

Sooo... i had the EGR cleaned. The mechanic worked all day on getting the EGR out of there but finally it's clean. BUT the problem still didn't go away.
wallbash:

I`m getting and exhaust back pressure reading of only 0.8 bar at key on - engine off and 1 bar at idle. Shouldn't the back pressure at key on-engine off be about the same as the barometric pressure (about 1 bar)?

 

[boyt]

Have you replaced the sensor yet?

Andy