V Klasse exhaust back pressure sensor issue

The symptoms you describe suggest a problem with the exhaust back pressure sensor. Before replacing it, inspect the sensor's wiring and connector. Corrosion or damage can cause similar symptoms. Did you check the wiring harness? Also, have you found any diagnostic trouble codes besides the warning light? A code related to the exhaust back pressure sensor would help.

Thanks. I glanced at the wiring but didn't see anything obvious. I only used a basic OBD2 reader, which gave me a generic emission control system error. Is there a specific code I should look for to confirm the back pressure sensor?

A more detailed diagnostic scan is a good idea. A generic emission control system error can have many causes. A better scanner should give a more specific code, like P0470, P0471, P0472, P0473, or P0474, which relate to exhaust back pressure sensor issues. If you find one of those codes and the wiring looks okay, replacing the sensor is a good next step. If you don't have advanced diagnostic tools or aren't comfortable doing the work yourself, see a mechanic. The price you mentioned seems reasonable, but get a quote from a shop to be sure, including labor.

I appreciate the advice. I took it to a shop, and they confirmed it was the exhaust back pressure sensor. They replaced it for 245€. The warning light is off, there's no more smoke, and the DPF is regenerating again. Thanks!