2002 2500HD 6.0 "Low Coolant"?

Through a gasket to inside the engine, through a gasket to outside the engine, through a crack to somewhere else, bad radiator cap, cracked coolant reservoir..... Pull the plugs and look for fouling, look around on the block and manifold for boiled coolant residue. Could be simple and cheap like a radiator cap, ..........or not. Should be under warranty anyhow. Luck

Don, I had the same thing happen to my 99 Silverado. I checked the tank and it really was not that low... I added a small amount of the coolent mixture anyway, problem went away?? They told me it could be a bad sensor? B.G.