Mini Countryman Diesel DPF Issue

That sounds concerning. Low pressure readings from the DPF exhaust pressure sensor could stem from several issues, not necessarily just the sensor itself. Have you checked for any visible damage to the exhaust system, like cracks or loose connections? A leak could certainly cause low pressure. Also, what kind of driving do you typically do? Short trips can prevent the DPF from regenerating properly, leading to a buildup of soot and potentially affecting pressure readings. It's possible the sensor is faulty, but I would proceed cautiously before replacing it without further investigation. Are you able to read live data from the sensor? What values are you seeing at idle and under load?

Thanks for your reply. I haven't looked for any physical damage to the exhaust, I will check that tomorrow. I mostly use the car for commuting, about 30km each way, mostly highway. I don't have the equipment to read the live data from the sensor, unfortunately. Is there a way to check the DPF regeneration process without special tools?

Okay, the highway driving is good, so it's less likely to be a blocked DPF, although it's still possible. Without being able to read the sensor data, it's difficult to say for sure. Checking for exhaust leaks is a good first step, but they can be tricky to find. Given the symptoms and the mechanic's initial diagnosis, a faulty exhaust back pressure sensor is definitely a strong possibility. It's probably best to get a second opinion and have the sensor properly diagnosed, perhaps with a scan tool that can read live data. Replacing it without proper diagnosis might not solve the problem, and you'll be out of pocket. I would advise getting it checked by a workshop.

Update on my initial post: you were spot on! I took my Mini Countryman diesel to a trusted mechanic, and it turned out to be a defective exhaust back pressure sensor, just as you suspected. The replacement plus labor cost me around 245€. No more warning lights, no more smoke, and the engine is back to its old self. Thanks again for your help!