GM-GMC: Oil pressure Gage, pressure gage, faulty sensor

Question
Why would my oil pressure gage shoot up to the Max's and stay  there

Answer
There are a number of reason that your pressure gauge is reading max.  One is a faulty sensor, another could be a faulty gauge, less likely but still possible is a shorted wire.  Without knowing what you are working on that is as accurate as I can be.
Hope this helps a little.