The needle lift sensor is built into the No. 1 nozzle. Its inductive
pickup element senses fuel injection timing. It is sent as a pulse
signal to the ECM for feed-back the actual fuel injection timing and
calculating the secondary engine speed.
I think its just the injector pump thats coded to the ecm.
IF YOU LOOK IN THE WORKSHOP DOWNLOADS THERE ARE ALL THE FAULT CODES IN THERE.
WHEN MY TDI HAD PROBLEMS I KEPT GETTING THE SAME 3 FAULT CODES 18 ,21 AND 22 I THINK WHICH WERE ALL FUEL RELATED.
Neither the pump or the injectors are coded to the ECU, you could try another injector to rule it out but be aware there are 2 different types, I think it depends what system you have either Bosch or Zexel.
Well afella thats worked with diesels since day dot has got the car now so if it breathes it stays and if it dont we got plenty of parts for sale but wont know til weekend