oil p. guage maxed out

2005 Sub 1500LT. I had the guage replaced a second time because I assumed it had gone bad again. Wrong! The guage sits at "0" until I start the engine, then pegs all the way over to max.

So...is that a fuse? Is it a bad wire? Or, is my sending unit bad or disconnected....and where is the sending unit?

Don't know the theory of operations of that one, but depending on the way it works that could mean that it's wire is grounded, or the sender is bad, not sure where the sender is on that one. The 2005, 6.0, 5.3, or 4.8?

They should all be the same anyhow, the sensor goes straight down into the front edge of the intake area right below the throttle body. The best first diagnosis would be to remove the sensor and stick an analog gauge in it's hole and see what the oil pressure actually is. The 'idiot gauge" is far from accurate, it is really just a switch....