ok i have a 2000 silverado 2500 with the 6.0 lq4...
i read my pcm as a 99-08 ls1, but when i go to reflash it will iniatialize through all 4 steps but then is kicked out and pcm goes to an unknown state.
i then did all the neccesary step to unhook the controller and watch the scan tool on the laptop and even it couldn't connect..
after trying to start several time to no avail would crank, and thats it. after going through gm books and internet surfing for a half hour i went to it and it started up with zero problems.
i dont understand, your help would be greatly appreciated and helping me reflash would be great this gas tuning is knew to me, im a diesel tuner and have never had this problem.

thanks