Toyota Tundra: How to Install Trailer Wiring Harness

Gonna take the wife and kids out for a great fishing adventure? First make sure your Toyota Tundra can handle the boat.

By August Barrett - January 29, 2016

This article applies to the Toyota Tundra (2000-Present).

Hauling your trailer or boat is a bit more complex than just hitching it up and going. We also have to account for the electrical side of things; ergo, a wiring harness is required. This harness matches up the lighting system of your trailer to your truck and hooks up to the factory connector. Time to install it on the truck so you can go pick up that boat. You have never installed a wiring harness before? Well, this here article will give you the knowledge and the confidence to get er' done.

Toyota Tundra How to Install Trailer Wiring Harness

Materials Needed

  • Adjustable wrench
  • Screwdriver
  • Electrical tape
  • Test light
  • Threadlocker
  • Zip ties

Step 1 – Install universal mounting bracket

First, attach the universal mounting bracket to the trailer hitch bar at the rear of the truck. Be sure to leave the bracket at a slight angle. Tighten the bolts a bit, but leave it a bit loose because there will be some adjustments later.

  • Multi tow wire harness
    Figure 1. Multi-tow wire harness for the Toyota Tundra.
  • Universal mounting bracket
    Figure 2. Tow ready universal mounting bracket.

Step 2 – Attach bracket to universal mounting bracket

Next you will be attaching the bracket that came with the tow package wiring harness to the universal mounting bracket. So, using the hardware provided, your screwdriver and adjustable wrench, connect the wiring harness bracket to the universal mounting bracket.

wire harness plug bracket
Figure 3. Wire harness plug bracket.

Pro Tip

Use a drop of Threadlocker on the screws. This will prevent them from coming loose.

Step 3 – Attach wiring harness

Insert the 7-pole connector into the bracket. You will need that monkey wrench to bend the bracket out from the bumper, as the back of the plug will hit up against the bumper. Screw the plug to the bracket and don't forget your Threadlocker.

7-pole mounting bracket
Figure 4. Bending the 7-pole mounting bracket.

Step 4 – Plug in and adjust bracket

Loosen the universal mounting bracket and position it so that it is easily accessible. Torque it down for good, as no further adjustments will be needed now. Now plug the harness in to the tow package port located underneath the truck. Make sure that the connections click. Take the other connector from the harness and tape it off because it will not be needed in this application.

  • connecting harness to truck tow port
    Figure 5. Connect harness to truck tow port.
  • taping extra connector
    Figure 6. Tape up extra connector.

Step 5 – Secure and test

Using zip ties, secure the harness out of the way by attaching them to existing lighting wires located under the truck. Using your test light, test the plug by inserting into each port individually while a friend engages the lights, brakes and turn signals separately. That's it, you are done. Enjoy.

Featured Video: Installation of Trailer Wiring Harness

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