1999 Chevy Suburban 5.7L 350Vortec High Oil Pressure?

Could be a bad oil pressure sensor or the dash oil pressure gauge is bad ....you can try a new oil pressure sensor but if that reads too high as well on the dash gauge, it could still be a bad dash gauge. The usual way or method to test it is to install a known working mechanical gauge to the oil pressure port on the engine and read/test what the oil pressure is at idle and higher rpm's....usually pressures run around 20-30 psi at idle but it can vary depending on where in the oil gallery the oil pressure port is tapped into and pressures usually rise by around 10 psi for every 1000 rpm's. So if idle oil pressure is at 40 psi, then by around 4000 rpm's it should be up to around 80 psi.

If the pressures read normal using the test gauge and you install a new oil pressure sensor and it still reads high or not the same as the test pressures on the dash gauge, then the gauge is bad.

Most likely it's a bad sensor but it can also be a bad dash gauge.

That's pretty normal for a 5.7L V8. Oil pressure is limited to 60 PSI by a pressure bypass either in the filter or in the oil pump itself.

More than likely the electric oil pressure sending unit needs to be changed. We're assuming you're still using the factory recommended 5W-30 motor oil.

Read the diagnostics codes.

what your gonna want to do is set it to wumbo. thatll fix it right up