Oil Pressure gauge stuck at 80 and how to test

This is a way to diagnose an oil pressure switch failure and not a stepper motor.

  If your oil pressure gauge on a 03-06 5.3l is stuck at 80 psi this is a easy fix.
First does the gauge go back to 0 with the engine off and key in the off position? If yes, continue by turning the key to the run position but the engine off, does the gauge go right to 80? If it does then turn the key to the OFF position and go to the rear drivers side of the engine and feel for the switch. Once found unplug the connector from the switch and repeat test. With the key in the ON position the gauge should read 0. Replace the Switch and test again.

Nice write up. I had to replace mine this summer. I think the hardest part was blindly reattaching the sensor wire.

It's kind of like the fuel pump replacement, drop the tank or cut a hole in the floor. Take the intake manifold off or do that.

Really depends upon how big your hands are.  I couldn't do it but the Mrs. could! 

I found that I could reach the sensor if I removed the cover and climbed on top of the engine and reached under the fuel lines.  I did how ever scratch the hell out of my arms and hands.