There has been a lot of discussion about this but to me the only way to locate the problem quickly would be to rig a calibrated direct reading oil pressure gauge into the oil system.
Once this is fitted run the engine on the ground and observe the pressure readings.
Compare the direct reading gauge results with the aircraft oil pressure gauge and the certified requirement ( TDS) across the engine RPM range.
This simple process will locate the problem system be it the engine or the oil pressure indication system.