Oil guage read 0 - turned off truck and bad main bearing

Excellent write up on "Idiot" lights explained: http://www.gowesty.com/library_article.php?id=810

That is for VW but should give a general idea. I don't have any information on GM and the parameters set in the code for oil pressure.

depends on what rpm 10 lbs per 1000 rpm...i win !!!!!

4PSI in my mind is way too late for a warning. Drove 100 ft and rebuild or replace according to dealer. Oil pump failed and the main bearing is pretty chewed up. In the early years I depended on the oil percentage and then switched to every 3000 miles using high mileage oil. Dealer wants $7100.00 for crate and $5100.00 for an engine with 81,000 miles on it. I am torn as what to do as this is the last truck I planned on buying. Have only put on 61,000 miles since 2008 when I was able to work from home. That is 7 years 61,000. Crazy - any recommendations... I am checking with local auto repair shops for a lower price. Just really ticks me off this has happened.

You may be ok. Did you hear any engine noise, knocking, ticking to indicate low oil pressure? If not I do believe there is a screen basket under the oil pressure sending unit that gets full of sh** that needs to be cleaned. Screen gets full of crap not allowing the oil pressure switch to read properly. Cheap Check...

Thanks for your help - no noise that I ever heard that would tip me off that something was wrong. The dealer showed me the main bearing that was chewed up pretty good. Truck is back at my house now going to have used motor put in from a local shop wth a 3 year 100,000 mile warranty.