GMC Troubleshooting Questions? Ask a Mechanic for Answers
I am sorry your having this problem
when a battery will go dead like this the odds are there is a draw on the system
has a draw test been done yet ?
do you have a multi meter on hand ?
what has to be done is a multi meter set to amps needs to be connected in series on the negative battery cable and see if the mili amp reading is 50 MA or higher if so and NOTHING is left on or nothing is one when it should be off inside the truck is one fuse is pulled at a time until the draw drops below 50 MA then what ever is on that fuse is causing the draw which on these the usual draws are the BCM or radio and a few with bad gauge clusters not turning off when the truck is off killing the battery