Need a 4-Pole Trailer Wiring Harness for a 2003 Toyota 4Runner with No Trailer Wiring

Question:

Hi, I have a 2003 4Runner with no trailer wiring harness whatsoever. I know this is probably a silly question but would it be easy enough to modify part# 118413 to fit my vehicle. Better yet, do you have such an item available ? Thanks.

asked by: Guy T

Expert Reply:

The TowReady T-One Vehicle Wiring Harness for the Toyota Highlander, part # 118413, is a vehicle-specific plug-and-play trailer wiring harness. Because it is made specifically for the Highlander, it offers the convenience of very simple plug-in installation without the need to cut and splice wires. However, it would be impractical to try to modify this Highlander harness for use in your 4Runner.

Although we do not offer a comparable plug-and-play trailer harness for your 4Runner there are hard-wire kits available. These include the wiring harness with 4-pole connector, a circuit tester for identifying wire functions, as well as the required wire, fuse and holder and quick-splice connectors.
Kit # C59236 will work with both domestic production and imported 4Runners and is compatible with LED lights (on either the vehicle or trailer). Since this is a powered converter that brings power for your trailer lights directly from the vehicle battery (rather than through the tail light circuit) it eliminates any risk of overloading the vehicle wiring. Still, it is a good idea to keep in mind the maximum current capacity of this harness, which is 3 amps per turn/brake circuit and 6 amps for the tail light circuit. If possible check your trailer manual for information as to how much current it will draw so you can be certain not to overload the harness.

I have linked a video showing a typical installation process. Although this video concerns a different vehicle the overall process on your 4Runner will be essentially the same as shown.

The installation process consists of tapping into the wiring at the two taillight assemblies and making one 12V power connection between the converter and the vehicle battery. The included circuit tester allows you to verify the function carried by each wire at the taillight assembly. Most connections will be made at the driver-side and just one at the passenger-side light for the right turn signal. The 12V power connection requires running the included power wire underneath the vehicle to the engine compartment (securing it with the included zip ties) and connecting it to the battery positive terminal with the supplied fuse holder and fuse.