DPF Cleaned but Engine Light - PeachParts Mercedes-Benz Forum

nyko46 · #1 05-12-2020, 08:15 PM

As I posted short time ago, my 2008 MB E 320 Bluetec was having a engine light with codes: P0471 and P242F.
P0471 for Exhaust Pressure Sensor Range/Performance and
P242F for Diesel Particulate Filter Restriction - Ash Accumulation.
For that reason I replaced the entire DeNOx, part # 450 (not 455) in the schematic and I had fully cleaned by a certified DPF cleaner company my Particulate Filter part # 640 in the schematic.
After everything installed in my car, the installer cleaned the Engine Light and the car drove very good.
Very soon after, the engine light came on again with the same codes that it was before: P0471 and P242F.
I heard many times that the car has to be driven a couple of the times to completely clear the codes from the ECU but if it is the case, it seems like it is taken too long to clear the codes.
I am driving the car now for around 220 Miles since DPF was cleaned and the engine light still on with the codes above.
The company that cleaned the DPF had it cut on both ends and then cooked for 8 hours and then reassembled and tested. According to then the Vacuum Pressure Differential was 6+ before and it is 1+ after cleaned.
They also said that the filter itself is in good condition with not damages.
The car is running very good with a good response to the throttle and no hesitation when torque is required.
Now I still having the question about why Engine Light and codes are present if the components of the Particulate Filter were taken care.
I appreciate any information about this issue that is going on with my
E320 Bluetec 2008.
Thanks everyone.

(Sorry, my schematic file is bigger than this site allow) It is a drawing # B49222000008 from MB

pawoSD · #2 05-13-2020, 12:36 AM

Those codes might need to be cleared or reset with the dealer scan tool/system, not all codes just go away on their own once triggered, even if the underlying cause is gone.

Could also be an issue with one or more of those sensors, they can and do go bad.

nyko46 · #3 05-13-2020, 08:26 PM

Quote:

Originally Posted by pawoSD

Those codes might need to be cleared or reset with the dealer scan tool/system, not all codes just go away on their own once triggered, even if the underlying cause is gone.

Could also be an issue with one or more of those sensors, they can and do go bad.

As for those two tubes that goes to the DPF, they are connected to some sensor, which I know as measuring the pressure differential before and after the gases pass through the DPF.
Can those two tubes and hoses get clogged? Since the tubes are in contact with the smoke and soot from the burned diesel, how can they not get clogged?
I am asking this to myself since I first saw that system on Mercedes.
Explain me please.
Thanks

pawoSD · #4 05-13-2020, 10:50 PM

I've never heard of them getting clogged, there's not really any "airflow" per say into the sensor or tube, its just measuring the pressure.

I have heard of the sensors themselves going bad though...as any sensor can after years of thermal cycling and use...the downside is that they are pretty pricey.

engatwork · #5 05-14-2020, 06:57 AM

I think it is called a differential pressure sensor and I have had to replace one before. Never seen any indication of pluggage in tube.

nyko46 · #6 05-14-2020, 09:52 PM

Quote:

Originally Posted by pawoSD

Those codes might need to be cleared or reset with the dealer scan tool/system, not all codes just go away on their own once triggered, even if the underlying cause is gone.

Could also be an issue with one or more of those sensors, they can and do go bad.

Today talking to the mechanic that removed and re-installed my DPF I was told that there is a hole of about 1/8" just in front of the DPF, before the gases reach the filter of the DPF. The hole is a very well made hole, which lead to believe that it was intentionally made.
Can this little hole give a false reading of pressure differential and lead to codes about DPF issues?
Also, is there a reason to have any hole in the DPF system?
Thanks

engatwork · #7 05-15-2020, 07:15 AM

It could possibly lead to codes. I'm thinking someone probably drilled hole to test back pressure.

jay_bob · #8 05-15-2020, 07:51 AM

No there is not supposed to be a hole in the exhaust!

I think that would be contributing to your problem with the differential pressure.