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  1. Custom Fit Vehicle Wiring
  2. Tekonsha
  3. Custom Fit
  4. Trailer Hitch Wiring
  5. 4 Flat
  6. Powered Converter
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

Item # 118701
Our Price: $54.13
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Custom Fit Vehicle Wiring
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Shipping Weight: 1.67 lbs
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Custom Fit Vehicle Wiring 118701 - Powered Converter - Tekonsha
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Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system. 1-800-496-5010 to order Tekonsha custom fit vehicle wiring part number 118701 or order online at Free expert support on all Tekonsha products. Great prices and Fastest Shipping for T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
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  • Reviews (7)
  • Q & A (0)
  • Videos (1)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118701

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • Powered Converter
  • Tekonsha

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.


  • Provides a 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights
    • Compatible with 5-pole, 6-pole and 7-pole adapters (sold separately)
  • Connects quickly and easily
    • Locate connection points in rear cargo area
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes ModuLite power converter to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects to battery to avoid overloading vehicle's electrical system
  • Constructed of 16-gauge bonded wire
  • Comes with dust cap for 4-way flat connector


  • Maximum amperage:
    • Stop/turn lights: 4.2 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • 1-Year limited warranty


This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located inside your rear cargo area, behind the tail lights on both the driver's side and passenger's side. You will have to remove the rear threshold and some interior lining to access this harness. Once you've plugged in the T-connector, run the hot lead up to your car battery. Connect the lead to the included fuse holder, and then connect the fuse holder to the positive terminal on your battery and insert the provided fuse.

Once installation is complete, the 4-way connector will be stowed in your trunk.

It is recommended that you use a small amount of grease on all electrical connections - the plugs on your automobile and the 4-pole connector itself - to help prevent corrosion.

Modulite Powered Tail Light Converter

A ModuLite power module is built into this T-One connector. Because most trailers run on a two-wire system - wherein the brake and turn signals are carried on one wire - the separate brake and turn signals from your vehicle's three-wire system need to be combined so they are compatible with the wiring system of your trailer. This power module functions as a tail light converter to combine the brake and turn signal functions of your automobile so that they run on one wire to properly activate your trailer's tail lights. Note: This will not affect how the tail lights on your vehicle operate.

With a ModuLite, your trailer's lights will be powered without overloading your vehicle's electrical system. Because the module draws power directly from your car's battery and bypasses the electrical routes that are used by a basic wiring harness, there is virtually no draw on your tail light circuits.

118701 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

Installation Details 118701 Installation instructions

California residents: click here

Video of T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Tekonsha Custom Fit Vehicle Wiring - Trailer Hitch Wiring - 118701 Review

Today we're going to look at the T1 Vehicle Wiring Harness with the 4-Way Flat Trailer Connector. This is a custom fit part, it is designed to fit the 2016 and newer Toyota Prius vehicles, and on a custom fit part I always like to recommend for you to go to our website, use our fit guide, put in your year and model vehicle and it'll show if this work for your application. Now this will again provide a nice 4-way flat trailer connector at the back of your vehicle to power your trailer's signal light. This will be compatible with 5-Pole, 6-Pole, and 7-Pole adapters that we sell separately. All this harness will connect quickly and easily. Basically just locate your connection points that are in the rear cargo area behind the taillight, plug in these two connectors, one on the driver's side, one on the passenger side, and then you have this remaining red T-connector here matched, and you'll run this underneath the vehicle on the driver's side, and match it to the T-connector on the vehicle, that is usually toward the rear of the taillight assembly, just plug it in right there. And then you'll want to ground the white wire, and then the black wire is your power wire, that will run to your vehicle's battery. Now this harness does include the module light here, this black box.

This is a power converter to ensure that your vehicle's wiring will match that of your trailer, and the power module will connect directly to your battery to avoid overloading the vehicle's electrical system. Now the wire that they run off the back with the 4-way attachment that plugs into your trailer, that wire is a 16-gauge bonded wire. If you notice on the 4-way, this does come with an integrated dust cover for the 4-way, so when it's not being used you can just put that cover over to protect the terminals from any damage or from the elements. A few specs on this harness. The maximum amperage is for the stop and turn light circuits is 4.2 amps per circuit, and for the taillight circuit is 7.5 amps. Now this part comes with everything shown here on the table, and again just briefly to go through how this would install, now they do give you a nice set of detailed instructions that'll describe how to install it, with pictures on where your connections are made. Basically again, you'll just go to the rear of the vehicle, the rear cargo area behind the taillights, and you want to start with the driver's side which is the T-connector has the yellow wire in it. What you do is go ahead and unplug the wire harness behind the taillights, plug this in to the harness in the taillight.

Then you'll take your other T-connector that has the green wire, that's the passenger side, you'll run that all the way over to the passenger side, plug that in right behind the taillights. Now the converter box, you don't want it bouncing around, so they do have a mounting hole right here if you want to attach a screw to hold it down. They also give you a nice piece of double face tape that you can use. And again you'll run this bonded wire out the back towards the trailer, and again the last connector is this length of red wire. Again, this will plug in to the matching connector on your vehicle, and that connector will be located underneath the vehicle on the driver's side, toward the rear of the taillight assembly. Once you find it that matches that, go ahead and plug that in. With the connectors all connected and the 4-way out the back, you have two remaining wires.

The white wire with the eyelet on it is the ground, you want to connect that to a good, clean ground. If there's one nearby you can use it, if not, they do give you a grounding screw that you can make your own. And then the remaining one is the black wire, that's your power wire, this is what'll run to your vehicle's battery, so they give you this extra length of wire to run that, and they give you these heat-sealed butt connectors, so you put one on there, one on the end of the length of wire, make your connection, run this all the way up to the front where the battery is. Now once you get up there, you don't want to connect this directly to the battery, you want to run it through the inline fuse holder right here. So what you'll do is take the other butt connector, connect it to one end of the inline fuse holder, and then on the other end of this fuse holder, you'll take this eyelet connector, and this is what'll connect to the battery. Once you get that all connected, just pop it open, take the included 15 amp fuse, line it up with the fuse holder, push it in, put your cap on there, and your system will be all ready to go. Now if you notice they do give you some extra cable ties that'll take up any slack in the wiring.

The large one they even give you, if you want to attach your power converter here with the cable tie either way. That should do it for the review on the T1 Vehicle Wiring Harness with the 4-Way Flat Trailer Connector.

Customer Satisfaction Score:

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118701

Average Customer Rating:  3.0 out of 5 stars   (7 Customer Reviews)

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.


DOA product! The DOA rate of the components inside this is virtually zero (FETs and whatnot), so this means Tekonsha's manufacturing process is bad (other people reviewing/asking questions have noted the same defect as mine) and their QA is non-existent. As with the other person commenting on this product, the brake lights don't work with mine (but turn signals turn on the same lights just fine). This is a safety-critical product so to me this is totally unacceptable. Buy the Curt product instead. I paid for an upgrade to the Curt as a replacement for my defective Tekonsha and it works perfectly.


I wanted to have my 2016 Prius II be able to pull a small trailer less than 1000 lbs. The kit is available but my local hitch installer would not do the work. I tried Uhaul they are only able to do the simplest of installations. So I bought the wiring harness kit from Etrailer and I will install it myself.


My vehicle is TOYOTA Prius AWE-e 2019
T-one connecter tekonsha # 118701 fit well on all connection. Only the signal light work. All other lights dont work.
How can i solve that problem?
Seam to have the same trouble as Paul on the review.


I wish I would have waited for the Curt product which was out of stock. The Tekonsha was wired wrong from the factory resulting in a cost to me of just under $300 for my mechanic to figure out the problem and wire my car. Without the defect it wouldn't have cost nearly that much.


The product was great but the directions were very vag as to where the plug was on the Prius. Turned out it was behind the brake light. But it took hours to find what they were talking about in the directions.


super friendly and helpful



See what our Experts say about this Tekonsha Custom Fit Vehicle Wiring

  • Installation of Wiring Harness on Toyota Prius
    The Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118701 is a fit for a 2016-2018 Toyota Prius so if that is your vehicle it would be correct. The connectors will have locking tabs that you need to carefully pry apart and it looks from your photo that it is correct. You will then insert the T-One T-connector end with the red wire between the vehicle wiring connectors and lock them into place.
    view full answer...
    Image 1 for
  • Tips for Routing Trailer Wiring Harness Power Wire on a 2017 Toyota Prius
    As far as a video or other media showing installation of the power wire on a harness such as # 118701 for your 2017 Toyota Prius we do not have any specifics. They are all generally the same though so you can follow the tips in the routing the power wire FAQ I have linked for you. Between it and the instructions I have also linked I am sure you will be able to tackle this project, no problem.
    view full answer...
  • Does Curt Trailer Hitch Receiver C11473 Include Vehicle Wiring Harness?
    The Curt Trailer Hitch Receiver - Custom Fit - Class I - 1-1/4" # C11473 you were looking at for your 2017 Toyota Prius Two does not include a vehicle wiring harness. You will need to purchase one separately using # 118701 as long as your Prius is not the Prime model. To finish your towing setup you will also need drawbar # C45521, 1-7/8" hitch ball # A-80 or 2" hitch ball # A-82, and hitch pin and clip # F-4. I included videos of the products mentioned for you to take a look at.
    view full answer...

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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Adam R
Expert Research:
Adam R
Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video by:
Joshua S
Employee Jonathan Y
Video by:
Jonathan Y
Employee Wilson B
Updated by:
Wilson B
Employee Isabelle B
Updated by:
Isabelle B
Employee Alexander C
Written by:
Alexander C
Employee Shane H
Test Fit:
Shane H
Employee Ryan G
Test Fit:
Ryan G

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