Hello Sidney, a blown fuse is usually caused by an over current situation in a particular circuit, in your case the ignition circuit. If you get a service manual, which i recommend, you will find where the wires run. You need to trace wires in the circuit to make sure there are no shorts to ground (where wire insulation is damaged and wire is touching bare metal). Hope this helps.
Search GMC Sierra 1500 Questions
GMC Sierra 1500 Experts