Problems with black smoke and loss of power in Mercedes S Class Diesel 2012 - suspected defective exhaust back pressure sensor

Hi, I had a very similar problem with my 20 Mercedes E Class diesel. I only have some car mechanic experience, but maybe it will help you. On my car, the DPF was heavily loaded, which led to similar symptoms that you mentioned. I then drove to my regular garage. The mechanic read out the fault memory and then carried out a professional DPF cleaning. This treatment cost me just under 1325 euros. After this procedure, the handling of my car improved significantly, the black smoke had disappeared and the engine was running smoothly again. However, without more detailed information about your vehicle, I can't help you in more detail. How many kilometers has your Mercedes done and when was the last oil change? Hopefully my experience will help you!

(Translated from German)

Hey, thanks for your quick reply! My Merc now has exactly 124,594 km on it. The last service was only recently, so everything should be in order. I was hoping that there might be a cheaper solution, but if professional DPF cleaning seems to help, I'll have to consider it. This is exactly the kind of experience I need, so thank you very much!

(Translated from German)

Hey, no problem, you're welcome! Your Merc already has quite a few kilometers on it and a DPF problem like this can certainly occur from time to time. With this mileage and considering your symptoms, your assumption about the exhaust back pressure sensor sounds plausible overall. In my experience, a defect or fault in the sensor would have led to increased fuel consumption - which you have also observed. And the fact that the engine performance decreases and the engine runs unevenly could definitely indicate a problem with the DPF. If you are worried that a professional DPF cleaning might be too expensive, you could perhaps check whether changing the sensor would bring an improvement. This will certainly cost less at first. But be sure to have the fault memory read out at the workshop. This usually provides the most information about possible problems. I hope this helps you and all the best for the repair!

(Translated from German)

Hello, thank you very much for your advice! I agree with you that it would make sense to have the fault memory read out. I think I really will change the sensor first and see if anything improves. If that doesn't work, I'll probably have to consider a professional DPF cleaning after all. Your experiences are really helpful for me, thanks again! I'll keep you posted on what comes out of the repair.

(Translated from German)