1998 chevy kodiak catapillar engine

Question

with a caterpillar diesel 6 speed would cause the code p0216 would it be oxygen sensor or af sensor I know it is injector/timing control module code and could be fuel pump or transfer pump inlet restriction, is transfer pump same as lift pump it could also be fuel filter restriction, or fuel injector pump gear alignment, or faulty fuel injection pump ? have changed fuel pump before, bled the fuel system and checked for air in lines; redid all battery connections and cleaned terminals still not wanting to start and run for long at all that is why wife wondered if it was a sensor like oxygen
but the af sensor has to run at hotter temp and if not it kicks in fail safe mode and shuts down. Any Input or help would be great thanks and yes I have done my own vehicle repair since age 10 I'm 50 now ...lol