your injectos should buzz each time the key turns on and if its buzzing that means your injectors and circuits are prob ok and now we need to know fuel pressure or if you have a scanner or can get a scanner we need to know the icp pressure
are you talking about the allen screw on the top side of the filter housing ?
p0603 test kinda leans towards pcm do you want the steps for each one of the codes and if you can do the test right that will lead you to your problem.if youhad access to another 2003 diesel you could swap the pcm's and try it
Note: Refer to the PCM and component connector pin numbers at the beginning of this pinpoint test.
Note: DTC P0606 may be set due to an intermittent engine oil temperature (EOT) sensor connector connection.
Note: Refer to wiring schematic for fuse number.