When my 98.5 gets warmed up, the oil pressure will drop to 0, idiot light comes on, occasionally when coming to a stop. The pressure comes back up after a few seconds. It acts as though its low on oil, like when slowing down there is not enough oil in the pan. Oil is full, 1000mi on oil and filter change. only does this occasionally. 270,000 on truck, original owner so i know the service history is good. Oil pressure sensor? blocked returns, oil not returning to pan? bad pick up? Getting ready to give this truck to my daughter when she gets her license at the end of the year, just want to make sure its good to go.

 

sounds like oil pressure sending unit is going bad.
put a temporary manual gage on...1/8 pipe plug on top of oil filter housing

 

Put a mechanical gauge on it to verify, but I would suspect a pickup issue.
Could also be a bypass issue.

 

mine did that on drive home in a snow storm, just kept going the pressure was good but the sending unit was bad, need to get one form a cummuns dealer the dodge people will rip you off. do a search they will try to send you one not like the one you have there is a direct replacement or was a couple of years ago. and you will probably good togo

 

I am a little skeptical you have anything more than a failing sender. If you are the Original Owner and have done diligent service you should be pretty solid inside still.

Go to a Cummins dealer and give the CPL number off of your engine ID tag to get the correct sender the first time. Some have three pins, some only two.

This number gives a perfect parts match every time and will save you some headaches.