I have a 02 Silverado with the 5.3 vortex engine. It will start and die in a couple of seconds. I have tried the relearn process and also the pass lock bypass but nothing seems to help. The security light was one all the time when I got the truck, but now after doing the relearn and bypass it only comes on when I open the door and goes out when I shut it. I don't know what to do from this point. Any help would be greatly appreciated.