My oil pressure started reading high one day, the next time I drove it, the gauge was all over the place, then the next time it went to where it would hit 120 with key on but not running. I checked the forums, and that last part seems to be typical of the sensor going out.

I got a new oil pressure sensor and had a buddy replace it. Oil level was fine, didn't bother hooking up a manual gauge to check the pressure because we were almost positive it was the sending unit. Now the gauge is setting right above 0. I had to get back to work, so I'm taking it back up there tomorrow. Any ideas what needs to be checked now, other than possibly the new sending unit is bad?

2004.5 with almost 80k miles, fully stock, if that makes a difference.

 

Did you replace the sensor with an OEM part or an aftermarket part?

 

I just picked one up at an auto parts store, so not Nissan.

 

electronics are best left up to the company that has liability concerns if they dont do it right. IE: OEM parts suppliers can lose their contracts if replacement parts dont work correctly. aftermarket parts manufacturers dont have that liability.
This especially holds true with electronics. I wont ever buy an aftermarket sensor/sending unit/relay/ballast/etc...