Several possibilities here .... ASSUMING A 4.2 ATLAS ENGINE ....
1. Bad sending unit -- but you won't see that value ....
2. Bad stepper motor ....
3. The pressure really IS low .....
4. The readout is telling you the truth - maybe.
1a. You don't really get a true picture of the operating pressure because the computer is reporting what the oil pressure SHOULD be under otherwise perfect and normal circumstances. If you saw the TRUE pressure, you'd shut the engine off immediately.
2a. If the little pointer you see in the gage nacelle is pointing to the wrong place - all by itself. It's lying. And broken. Test it by shutting the engine off and turn on the ignition (KOEO)... it should be at ZERO.
3a. This is a possibility - but usually wrong unless you hear the rods trying to swap positions inside the engine.
3b. The pressure may truly be low --- but not low enough to hurt things internally--- but it's right on the critical edge of doing so and MAY NOT make any untoward sounds until something goes ka-BOOM.
4. THIS must be tested .... if it says so, I'd believe it until proven incorrect.
It's a PITA to run a mechanical gauge on this engine -- but it can be done. It SHOULD be done, is more like it.
Are you capable of performing that test?
In case I missed it - and I'm not gonna go back and re-read your question --- what was the Year - Make - Model - Engine Size - Codes being reported for your vehicle..... ?
There's always the possibility of a bad wire or connection -- we will hold Ding Dong School about that in future posts ... make Miss Francis proud!
{1953 Chapter of Ding Dong School
HERE}