I have an s class 320cdi 2002, it has a fault code P1187.
Rail pressure monitoring deviation Can anyone help please.

 

Hi, I checked W163 Star Manual for 2002 ML320 which should have same engine. Code goes only up to P1186 Safety fuel shutoff detected: Throttle valve actuator sluggish/sticks Check intake train for residue.
Rail pressure deviation could be as simple as clogged fuel filter or momentarly fuel pump mulfunction. Sorry that I can't help any better.
Bernard