just a FYI. don't buy a acdelco sensor on Amazon. to many fakes to rule out a bad sensor even after replacing it. (I made this mistake twice) places like rock auto or the dealership still seem to be safe.
also it really helps to read the actual oil pressure from a scan tool. the gauges in these trucks are very general. while it might be low, it's honestly probably within gm specs with a known good sensor, clean screen, fresh old, I do like the thicker idea above and reading the actual pressure the ecm is seeing.
after that the next step is to check with a mechanical gauge. and then it's up to you where you go from there repair wise.