I had problem with a 06 Envoy Denali XL with 5.3 that the truck would not start, nor release the key from the ignition
. I found ING A #34 40AMP fuse blown under the hood, in the fuse service panel .When I replaced the fuse it just blew again
!I knew it was a shortage some where so short story is I did some troubleshooting .I found the metal shield plate on the starter rubbing against the hot + run battery cable wire that attach the starter! Check the shield plate you don't have to remove the start to complete this task!