There is a fuse marked "TRL TL" or something like that in the fusebox under the hood. It stands for "Trailer Tail Lights", meaning marker lights. It gets power with your parking lights and headlights. There is also one for the trailer brake lights, marked something like "TRL BRK". I've had it pop a few times before when inserting a 7-blade plug. If the terminals are corroded or the plug is too tight of a fit, you have to wiggle it back and forth, and I think that causes it to temporarily arc and short.