As I said in your last thread… just turn your ignition on , use the black wire from the sender, look through the rear window at your oil-pressure gauge and touch bare metal- ground momentary with the black wire… needle moves- sender bad..
very simple…
those gauges are not very precise… (you can cross reference with a mechanically gauge) But it gives you an idea where it should be normally, and if it deviates from that, you know you have a problem..
also you can check with an ohmmeter if your sender has ground… again very simple..