i have a 2002 gmc serria 2500hd 4x4 6.0. will not stay running. i have gas coming to motor. i go to start it and it runs for a min then stops. i did the the procedure of the 3 times 10mins to relearn. i even replace the ignition cylinder today and that didnt work after i try to relearn it again. anyone got any ideals? i just dont know where to go from here.. help!!