Volvo C70 diesel particulate filter issue

That low exhaust pressure reading combined with those symptoms definitely points towards a problem with the exhaust system. The sensor is a good place to start. Have you checked the wiring and connections to the sensor itself? Sometimes a loose connection can cause false readings. Also, is the DPF itself relatively clean? A clogged DPF could cause similar issues, though usually with high pressure readings.

Thanks for the quick reply! I did check the wiring, and it seems okay, no obvious damage. I haven't been able to check the DPF. I don't have the right tools. If the wiring is fine, does that pretty much confirm it's the sensor, or is there anything else that could cause low pressure? I am also a bit concerned because of the smoke.

While a wiring issue can cause it, if the wiring seems fine, the sensor itself is the most likely culprit given that fault code and those symptoms. A faulty sensor wouldn't correctly read the pressure which could cause the ECU to not inject the correct amount of fuel. That would lead to excessive smoke and poor performance. I'd suggest taking it to a trusted mechanic. They can confirm the sensor and check other parts. Best to get it sorted before it causes further damage to the DPF or turbo.

Okay, thanks so much for the advice! I took it to a local shop, and you were spot on – it was the exhaust back pressure sensor. They replaced it, and everything is running perfectly now. Cost me about 245€ all in. Really appreciate the help!