Mini Countryman diesel issues

The symptoms you are experiencing, such as engine stalling and reduced engine performance, certainly suggest an issue with the fuel system. The 'faulty rail pressure sensor signal' error is a strong indicator. To confirm, were any other error codes present during the diagnostic check? Also, has the fuel filter been recently replaced, or is there any evidence of fuel contamination?

Fuel filter is fine, no contamination, and the error code was definitely about the rail pressure sensor. I'm just trying to get my head around what this sensor actually DOES and how it can cause all this chaos?

Indeed, the pressure sensor monitors the fuel pressure in the fuel rail. If the signal is erratic or absent, the engine control unit (ECU) receives incorrect data, potentially causing the issues you described. Think of it like a faulty thermometer telling you the oven is cold when it's actually scorching. The ECU then makes incorrect adjustments to fuel delivery, resulting in poor engine performance and stalling. Given the error code and symptoms, a defective pressure sensor is the most probable cause. I would advise consulting a qualified technician for sensor replacement and system recalibration.

Big thanks for the input! Turns out you nailed it. I had the pressure sensor replaced and that sorted everything. Cost me 240€ but now my Mini Countryman is running sweet again. What a relief!