Have 2001 Ram 1500 5.2l and check Gauges light came on, on deceleration and oil pressure went to zero. Increased RPM's and pressure goes up and light goes out. Took to dealer and they replaced radiator, thermostat and oil sending unit.
Next day light came on again-same on deceleration. Took back to dealer and they replaced oil pump, the pickup tube and screen.
Next day--same thing--
Shop checked out again and stated they installed manual oil gauge and ran until check gauges light came on again, and manual gauge showed good pressure.
Shop states that it is the PCM now.
Does that seem reasonable, or are they just guessing?

 

I think they are just guessing. Their scanner should be able to tell them what the PCM thinks oil pressure is. I would be more inclined to believe they installed a bad sender (yeah, right out of the box), and would want to try that first.