I have a 2008 Sierra with the 5.3. I have 70000kms on it now. Once the engine warms up a bit it starts to get a rough idle. The rpm's go up and down a bit but I also notice that the oil pressure gauge fluctuates. The truck does run good except for that rough idle. When I bought the truck I had told the dealership to check that out before I picked up the truck but they did not. I was hoping that I could get some direction into what I might be looking at. The truck still has warranty but I would try to figure out the problem before I take it to the dealership since their usual answer is "We can't find nothing wrong". Rick

 

Might check to see if the oil sending unit is bad or has a bad wire connection. If your truck reads 0 psi, I think it will shut fuel off to prevent engine damage, so that may be whats happening.