2005 Td4 146k miles.
i have a lumpy tick over and engine sometimes cuts out when sat in traffic when upto full temperature.
diagnostics comes up with fault code ..... P0191 rail pressure offset test
would this point towards either the fuel rail high pressure sensor and/or the wiring harness , its not had the new overlay harness fitted but if i wiggle/push the connector the lumpyness stops or isn't quite so bad
many thanks for your thoughts and help

I think you may have solved the problem your self, as you say moving the connector tend stop the rough tick over, this would indicate that the wiring is breaking down, try a little spurt of electrical contact cleaner in the end of the connector on the fuel rail, pushing it on & off a few times see how it performs after that, but is does sound like you may need the overlay harness ?

thanks for that Arctic , guess i was just looking for a second opinion, if the harness cures my problem will post it here

I had the very same problem on a 2005 TD4 we bought at the weekend. Did some reading up and ended up unplugging the sensor and spraying a load of contact cleaner in it and when dry some WD40. Connected it back up and now running absolutely fine
The post I read said to first unplug the sensor and then start the car with it unplugged and if the tick over is fine then the sensor is the issue. This is what I did and the car ticked over great with the sensor unplugged so cleaned it and all is well!