2003 Pontiac Bonneville oil pressure at 120

[cking]

the oil pressure gage on my 03 Bonneville SSE goes all the way to 120 when cars running. Were is the sending unit at.

[ProTech]

The oil pressure sending unit is on the back of the engine block towards the passenger side of the car. That may or may not be your problem, though.

You could have a faulty gauge, or the wiring between the gauge and sender could be shorted/corroded/cut. A proper way to test would be to start by doing an actual pressure test with a gauge in the oil port the sender is screwed into. If that reads normal, you may want to start with an oil pressure sender since they aren't too expensive and are fairly easy to replace.

If it ends up that the actual gauge is malfunctioning, the entire instrument cluster would need to be replaced and programmed.

[carriedi]

does it go all the way back down when you turn off your key? If the gauge doesn't go all the way back when the key is off the stepper motor for the gauge may be bad. It could be replaced but they are soldered in. (usually) If you know someone with a scanner you could do a sweep test of all the gauges and see how it reacts. If it works normally then you would look at the wiring out to the motor.