Several years ago, my 2005 GMC truck would be going down the road and just shut off like you killed the ignition with no codes. It usually would then be able to be restarted immediately. It gradually started happening more frequently as I checked fuel pump pressure, etc. It would always start normally when cold and then start acting up as it warmed up. I chased that problem for 2 months with the truck eventually becoming undriveable, including taking it to the sharpest GM mechanic in the area. Of course, the two days he had it, it ran flawlessly and then quit on me on the way home from picking it back up. He basically told me that I was capable of the same diagnostic steps as him and it would be a waste of my money to continue to have him troubleshoot. He did loan me a set of 4 known good coil packs to swap out each bank individually. The coils made no difference so he told me to start tracing wiring harnesses to look for any cuts or chafing. It ended up being a piddly little ground wire that ran from the PCM to the drivers side of the engine block. The wire was still connected by only 1 or 2 strands of the wire. Crimped on a 10 cent wire terminal and truck ran good as new. Apparently, when the PCM loses power due to a bad ground, that doesn't generate a trouble code. The good news is that was probably seven years ago and the old girl has ran flawlessly ever since. I do have to admit, the 6.0 gas motor's power and torque are on another planet compared to my son's 2000 Ram 5.9 and gets the same pathetic gas mileage. If I was a GM guy, I'd grab a junkyard LS, throw it in whatever vehicle I could find, and drive the wheels off of it.