GMC Troubleshooting Questions? Ask a Mechanic for Answers
under the hood, does IGN B 40amp fuse have 12.6 volts, its the power for the ignition switch?
Remove the fuse, OHM test the fuse across both tabs to see if its good. Then connect your meter to the negative battery post and then to the pins at the removed fuse to check for 12.6 volts.