At 38,000 miles: While driving, the engine began knocking, vibrating and shut off. The check engine light came on and the vehicle could not be restarted. It was towed to the dealer who diagnosed it with lifter failure. It was still under the powertrain warranty at this time. Several lifters were replaced as well as other engine parts and I was given the truck back after a few weeks. A week later, truck would not start. After looking under the hood I noticed most of the hoses and wires were not clipped off, causing them to just rattle and move around. Upon further investigation, I found that the wire to the starter was loose and had to be wiggled to get the truck to start. This wire should have been secured to the vehicle with the provided clips, but it was not and came loose because of it. I also found a random loose bolt lying in a void space under the hood near the windshield. I took the truck back to the dealership that replaced the lifters and explained my frustration with the condition my truck was put back together after tearing into the engine. I also showed them the random bolt I found. Their manager assured me that they would go through the engine compartment and make sure that the wires and cables were properly secured to the side like it should have been after the initial engine work. I never received an explanation of where the random bolt came from. After this engine work, my truck never seemed to drive the same. It began use more oil and the fuel MPG decreased. I reported to the dealer on the oil consumption and they had me start an oil consumption test. 600 miles after the oil change my engine light came on, truck began to run rough and make a loud engine rattle noise. I took it back to the dealer for a diagnosis. They called back and said that there was a lot of metal in my oil when they drained it. They contacted GM and are scheduled to open the engine up to find out if it can be fixed or needs a new engine. Currently at 52000 miles