Oil pressure

It possible the gauge in not working. See if you can hook up an external oil pressure gauge to verify you have oil pressure. If its still the same you may want to check your oil pump and or screen it may be clogged with slug.

On some of these vehicles there is a screen under the oil pressure sender. Remove the sender and look for a small screen. Clean the screen and while you have it apart install a new sender. I recommend buying the sender from a Chevrolet dealer. There is also a screen on the oil pump pickup pipe inside the oil pan, but I think the problem is more likely the sender, sender screen (if equipped) or the oil pressure gauge and or wiring. If the screen inside the oil pan were to plug you would hear clattering at the lifters when they were collapsing due to lack of oil. Do some reading at the link..http://www.gm- trucks.com/forums/topic/169782-attention-anyone-with-oil- pressure-issues/