I think that the oil pressure is switched from high to low when the engine temp reaches a certain point.
I have a 2013 Ram with that engine. I can watch the oil pressure and temperature on my dash screen.

74 Challenger, bought it new. In 1978 I replaced the original 318 with a 446 and 727. Mild cam, Jardine headers, and Holley Sniper EFI.
New engine! 511" RB, Edelbrock Performer RPM heads, Eagle rotating assy, Comp hyd roller cam, Doug's 2" headers.