Make sure that the wiring harness is properly grounded. Baring that, there is probably a short in the wiring somewhere. A short means the two wires used in trailer lighting are touching someplace.
Your local auto parts store can sell you a trailer plug harness that plugs into the vehicle's original harness that requires no cutting.
Check your fuses and look for a dead-short on the tail light wire (probably brown).
Auto parts stores can sell you a trailer harness that plugs in between your existing truck harness. The electrical connection used is usually located behind the rear bumper on the inside of the left frame. Directions will come with the trailer harness kit.
Probably the functions, running lights, reverse, brake, blinker, and a ground.
Plug in the trailer harness into the 7 pin hookup next to the receive hitch if you have a stock towing package.
The tow bar comes with a color coded wiring harness. The tail lights, blinkers, and brake lights are hooked up to a terminal near the trailer hitch of the towing vehicle and then the tow lights are plugged into the socket for the car lights. There are four wires. The brown is the brake lights, the green and black are blinker lights, and the white wire is the ground wire.
Yes, on a 2001 Tacoma it was a blown 5 amp fuse in the separate harness dedicated to the trailer lights. I did not realize Toyota Tacoma's came with a separate harness and fuse block just for the trailer lights/harness (this is separate from the under dash (#1) and under hood (#2). On a 2001 Tacoma , it located underneath the driver's side rear jump seat next to the factory tire jack.
U-Haul sells a kit with instructions
very easy .I bought my wires on eBay ,,,the trailer harness plugs right into your lights no cutting at all
The factory wiring harness for the trailers will plug in under the back of the vehicle in the area of the spare tire, the harness plugs into the wiring harness for the tail lights.
If there is a trailer wiring harness on the vehicle for towing unplug harness under drivers side rear tail light to eliminate the trailer wiring that's probably the issue then plug factory wires together
Brake pedal switch, wiring, bulbs, bad trailer harness (if there), fuses...