1. Under the hood, in the fuse block near the battery. Look for a fuse labeled "TRLR BRAKE" or "TRAILER."
2. Inside the cab, on the driver's side kick panel. There may be a fuse block located here, with a fuse labeled "TRLR BRAKE" or "TRAILER."
If you can't find the trailer brake fuse in either of these locations, consult your vehicle's owner's manual for more information.