Mercedes R Klasse Diesel Rail Pressure Sensor Problem

Sounds familiar. I had a similar issue with my old Vauxhall Astra. The fuel pressure sensor was giving me grief. Check engine light, limp mode the whole nine yards. Have you checked the wiring to the sensor? Could be a loose connection or corroded terminals messing with the sensor signal. What diagnostic codes are you getting?

Good point about the wiring. I did a quick visual inspection, but didn't get too deep. Where should I be focusing on the wiring harness? Any specific points that are known to be problematic? The error code is P0087 - Fuel Rail/System Pressure - Too Low. Does that align with your experience?

P0087 confirms low fuel pressure which points to fuel rail sensor. On my Astra, it was the connector itself that was the culprit. The pins were slightly bent and not making good contact. Given the mileage on your Mercedes, corrosion is definitely a possibility. I chased that issue for a week before taking it to a workshop. They sorted it pretty quickly.

Thanks for the tip. I wiggled the connector, cleaned the terminals, and nothing changed. So, I took it to my mechanic, and you were spot on! Turns out the pressure sensor was indeed defective. They replaced it, cleared the codes, and the car is running like new! The repair set me back 240€, but it's worth it to have my R Klasse back. Thanks again for your help!