A point of reference -- the parts for the oil pressure sender (for the factory gauge) from a 200TDi will work on a 300TDi. The only modification required is to trim about 3mm off the threaded part of the extension, P/N ETC4033, so that it does not bottom in the oil cooler housing.
You also need 4 copper or aluminum sealing washers.
To install -- remove the oil warning light sender from the oil filter housing. Install ETC4033 and ETC4034, providing two install ports for senders. Install your oil light sender on one port, and the oil pressure gauge sender to the other port. Connect wires, job done.
[appropriated from Ren Ching] Most faults can usually be traced to the badge on the grill.
Originally Posted by chris snell
This is straight out of the Manual for Build Builders.