S40 Diesel Smoke and Warning Light

I drive an S40 diesel too and had something similar happen. Are you getting rough idling or worse fuel economy along with the smoke?

Yeah, the idling's a bit rough, and I'm burning more fuel. Did changing the exhaust back pressure sensor fix everything, or were there other problems?

Sounds like what I experienced. I'm not equipped to do these repairs myself. I'd suggest a good workshop diagnose it. For me, it was the exhaust back pressure sensor, and replacing it sorted the problem.

Thanks for the tip. My mechanic checked it and confirmed it was the exhaust back pressure sensor. A new one cost 245€, and it's running great now. Your experience really helped!