Mercedes C Klasse diesel DPF warning light

I am familiar with DPF issues. I drive a Mercedes as well, though not a C Klasse. I once experienced similar symptoms: the dreadful warning light, a noticeable decrease in engine power, and that acrid diesel exhaust smell is something you don't forget easily. If the diagnostic code explicitly mentions low exhaust pressure related to the particulate filter, the exhaust back pressure sensor is a strong candidate. Think of it like this, the sensor is not correctly informing the car's computer about how full the DPF is, it is like a broken fuel gauge. Has the car been attempting DPF regeneration lately? When was the particulate filter last inspected?

Regeneration? I'm not sure. How would I know? Where is the sensor located?

If your vehicle isn't completing DPF regeneration, soot builds up, and the car will try to compensate which explains the reduced power and smoke. Regarding sensor location, it’s typically near the DPF itself, somewhere along the exhaust system. I would recommend a mechanic check it. The sensor is faulty in many cases. I had a similar problem and after the replacement and a forced regeneration, my car was running like new. The repair set me back around 245€

That's really helpful! I'll take it to a workshop to get the exhaust back pressure sensor checked. Sounds like that's the most likely culprit. Fingers crossed it solves the problem, and thanks for the price estimate! It ended up costing 245€ for the sensor replacement. Car is running smoothly now.