Mercedes W212 low exhaust gas temperature during forced Regen

[N Gupta]

Hi members,

I have a W212 Mercedes 2015 done around 66K miles. The car has always been services at the dealership. This year in March the Mercedes advised to update the diesel software and I agree to it in March. The car hardly does 3K to 4K annually due to pandemic (2020 and 2021) but I do make sure that I take it on a drive to Edinburgh and as well, did around 700Miles during our trip to north of Scotland in summer this year. Shortly after coming back from Holiday, the EML light (Amber) came up (First in August and then in October) and got the Mercedes Roadside assistance to look at the issue. The issue came up as DPF over 100% full and they did the force regen to get it down to 70% and cleared the faults. They did say that the the during the manual DPF regen, the exhaust gas temperature was not going up beyond 250° C. I have also noticed that the car is not going into the auto dpf regen mode.

After going through various threads, there is no advice that I could find on the specific issue. However, I have read various posts on DPF issues. Most of them point to the differential pressure sensor fault. The car is going to the dealer next week but it will be good to get an expert view on what could be the potential problems as Merc may just do a regen and mark the issue as fixed.

Any help is appreciated.

Cheers

 

[alexanderfoti]

If it did not go above 250, then it did not reach the correct part of the regen program.

It is not possible to do an in place regen, they must drive it on the road, so it sounds like they did no carry it out properly

also, a modern diesel should not have these problems, even with low mileage (unless you are going 2-3 miles then stopping).

Usually, blocked DPF's are a result of a mechanical fault, boost leak, injector fault etc.

The car will not regen with the light on, by itself.

 

[N Gupta]

Thank alexanderfoti for the quick reply. The roadside assistance engineer did take the car out for the drive and can back in roughly 40mins. He also said that there were no other faults except the dpf over 100%. From memory, i think it was around 106% full. I was asked to describe the service centre that the exhaust gasses is not going beyond 250deg C