Toyota 4Runner 1996-2002: How to Install Trailer Wiring Harness

Owning a Toyota 4Runner allows you to tow trailers, but you're not going anywhere before installing the wiring harness.

By Bassem Girgis - February 12, 2016

This article applies to the Toyota 4Runner (1996-2002).

It is an amazing thing that you can tow a trailer with your Toyota 4Runner; a benefit most car owners don't have. But before you start towing, you have to understand that without a wiring harness, you will get a sizable ticket. The wiring harness allows your trailer's brake lights and taillights to work with your car. Without it, you can be faced with a ticket. Installing a wiring harness could be complicated, but thanks to technology, now you can buy a wiring harness that connects to your taillight, which then takes power directly from it. Read on to learn how to get your trailer wiring harness going in the Toyota 4Runner.

trailer wiring harness
Figure 1. Trailer wiring harness.
Toyota 4Runner How to Install Wiring Harness

Materials Needed

  • Wrench
  • Phillips screwdriver
  • Trailer wiring harness

Step 1 – Disconnect negative battery terminal

Use your wrench to disconnect the negative (black) battery terminal. Wrap it in a towel so it doesn't touch any metal components and cause a spark.

toyota 4runner trailer wiring harness DIY how to
Figure 2. Disconnect negative battery terminal.

Step 2 – Remove tail light assembly

Use your Phillips screwdriver to remove the two screws holding the tail light in place. Give the tail light a gentle tap to the outside to pop it off.

toyota 4runner trailer wiring harness DIY how to
Figure 3. Remove tail light.

Step 3 – Install trailer wiring harness

The trailer wiring harness should have three ends: one attaches to the light bulb, one attaches to the harness that the bulb used to be attached to, and the third end is what attaches to the trailer's wiring harness. Remove the light bulb, and install it on one end of the harness, then install the second end to the electrical harness that was attached to the bulb. Feed the whole trailer wiring harness through the tail light assembly hole, and down. You will have to feed it through the liner until you see it from the bottom.

toyota 4runner trailer wiring harness DIY how to
Figure 4. Connect one end to bulb, one end to bulb's electrical harness, and feed the third end inside.

Step 4 – Install tail light

Install the tail light in place by tightening the two screws holding it in place. Then use whatever clamps that came with the trailer wiring harness to attach it to the frame, leaving the end of it, which attaches to the trailer's wiring, accessible.

toyota 4runner trailer wiring harness DIY how to
Figure 5. Attach harness to frame.

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