This issue has been really bugging me for a while and I cannot figure out what the problem is. The gauge is reading way past the 60/80 PSI mark on the gauge face. I reads about half way between the last mark and as far as it goes when the oil pressure switch is unplugged. This used to be an intermittent problem, but now it does it all the time.

GM does have a bulletin out about this problem and it says to replace the switch, but that didn't do anything. According to the wiring schematics, the orange wire is hot all the time, the tan wire goes to the gauge, and the grey wire goes to the fuel control. I used a test light today and the orange wire is indeed hot all the time, and then I put the test light on the positive side of the battery and both the tan and grey wires are going to ground as they should. I don't have a DMM so I can't check actual resistance on any of the wiring or from the switch.

Does anyone have any ideas on where I should look next?

 

i have the same problem, at idle it reads ok anything else and it jumps up of the dial. i just ignore it, lots of cars dont have them and you wouldnt give a second thought to it if you had one of them.

 

I know lots of newer cars don't have the gauge, but the PCM still monitors oil pressure and a message comes up in the message center if it is low.

 

There is no way you can check ANYTHING else without a DMM. Go out to Sears or somewhere and get a cheap one. It may not be accurate as most, but it will be in the ballpark of what the reading actually is. Since you already replaced the sending unit, the problem lies in either the wiring or the gauge, and both need a special tester to test properly, but you can at least use the DMM to see if you have a fault between the wire and the gauge. I have the same problem intermittently, but my problem lies in my sender's connector and wiring, where I adapted the new connector to my older system.