What does the switch (above the oil filter) actually do?
The switch is an on off switch, opens with whatever they deemed "adequate" pressure and closed below that point. I suspect the PCM looks at engine temp, RPM and other pertinent parameters and generates a theoretical oil pressure to display on the cluster gauge. It does thie by sending a message on the serial data bus that the cluster processes and displays on the oil pressure gauge.
I intend to pull one or more switches at the yard and test them to see where the setpoint(s) are.