There are two fuses under the hood that supply main power to the lights, they are main fuse #41 (100 Amp) and fuse #48 (30 Amp). Power travels to the fuse box in the passenger compartment to fuse #30 (7.5 Amp) this powers the dash lights and instrumentation, fuse #32 (7.5 Amp) supplies power to the side lights, tail lights and license plate lights. Start with the simple things does the fuse blow instantly, or does it only blow instantly, or blow when you go over a bump or open the tailgate?
Remove the rear tail light bulbs, license plate bulb, and marker lights ensure the correct type of bulbs are fitted and the bulb sockets are not corroded and causing a short. The wire that carries power to all rear tail lights, marker lights and license plate is colored red/green, look to see it is not pinched or shorting any where.