2011 Chevy Silverado 1500

Ok so I'm a mechanic and work at a used car dealership, just got a 2011 Chevy Silverado in from auction, got it on the flatbed and brought it to our shop. First time trying to drive it, I had to floor it just to get it to go 2mph. Hooked the scanner up to it and while I was doing so the truck lost all oil pressure as soon as it got up to temp and in fear of damaging the engine my boss made me shut it off before the scanner could finish reading all the codes. So I can't get all the codes in time, and I can't test drive it or leave it idling long enough to hear if it'll make any obvious tapping or knocking noises that occur when oil pressure is actually low. So all that factored in, what should I do? What can I do?

Is pressure being monitored via the sensor, or an actual, reliable mechanical gauge connected to the oil gallery?

I would also hesitate runing it until verifying oil pressure.