Has anyone ever ran into the oil pressure gage reading 40 psi all the time when the key is on? The engine not running and still reading 40 psi on the gage in the dash. Drops to 0 when the key is off, already replaced the pressure sensor and no change with issue.

When did you replace the sensor? I just did mine within the last month or so because I had pressure with the key on as well, and then once running the needle stayed around 60-70 the entire time. I also had high and low voltage codes for the sensor. Is the dash showing codes or any stored in the ecm/pcm? For me, a new sensor fixed the gauge issues immediately, but both codes took over 1,000 miles of driving to clear themselves.

Mine does exactly what the OP says his is doing. 40 psi all the time and I have a code of P0522 I believe to go with it. I think thats the low voltage code for the oil pressure sensor. I have a mechanical gauge for oil pressure anyway so I havent bothered with replacing the stock sensor. I would bet that it is the sensor that is bad on yours OP.

I just replaced the sensor yesterday. Didn't show any codes with the key, haven't had the scanner to check that way yet.