Isx oil pressure drops when let off throttle

[Kevinb3373]

New member, need help. I have had 2010 prostar with cummins isx for 3 yrs. 778000 miles, have done the egg, dpf delete.

Just got oil changed Monday, have run 1500 miles, on wed my red triangle and stop engine warning came on in display when I came to a stop light or getting off of highway. After I pulled over, stopped engine, waited 5 min, turn it back on, start it up and triangle is gone.

While cruising highway speed of 62 at 1400rpms pressure was 38,39psi. Then dropped to below 20 when stopping. Full of oil also.

Pressure sensor, relief spring? Oil pump? I've read so much info on here my head hurts!!

Where should I start, filter change?, sensor? Gauge? Should I even drive it

Thanks