A few ideas here:
Install an mechanical oil pressure gauge on the oil galley and measure the actual pressure, get a real number.
Anyway, sounds like your oil pressure switch is telling you the oil pressure is low, could be the switch is bad or associated wiring to the switch as well. Not sure if that's normally open or normally closed circuit off the top of my head but my guess is normally open circuit so if you disconnect the connector from the switch the problem may not show up anymore. If that's the case your oil pressure is probably too low.
Or jumper the harness connector if the circuit is normally closed(also possible).
This test will isolate the MPEM from being able to monitor the engine oil pressure, so it cannot generate the fault b/c it won't be able to see the fault.
But the engine will eventually be damaged if the oil pressure is too low, so measuring the actual pressure using a pressure gauge is the best course of action in any case.