Oil pressure gauge problems

[SemiSweet]

Are you sure the sending unit is a genuine oem Cummins replacement with matching part #? Not an eeBay/Aamazon lookalike? I tried to save some doll hairs once and bought a MAP sensor off eebay and with the key on the damn thing read 4/5 psi manifold pressure lol. Threw that thing right in the garbage.

I’ve seen this with oil/coolant temp sensors as well . They can have different working input/output ranges which don’t correlate with the gauge itself.

I have a little mighty vac hand pump kit which has a bunch of fittings and a mechanical gauge on it. You could use something like this to verify the pressure sending unit.