no CEL (check engine light)?
try this:
park the truck and turn the key off and remove from ignition.
put key back in and turn to the 'ON' position.
see if the needle readout for the oil pressure zeros out when the key is out and goes anywhere when you turn the key ON
try this:
park the truck and turn the key off and remove from ignition.
put key back in and turn to the 'ON' position.
see if the needle readout for the oil pressure zeros out when the key is out and goes anywhere when you turn the key ON