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

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

Item # TK99FR
Our Price: $57.98
You Save: 38%
Custom Fit Vehicle Wiring

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Shipping Weight: 0.82 lbs
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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 TK99FR 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.
  • All Info
  • Reviews (189)
  • Q & A (0)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - TK99FR

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • 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 behind the trim panel near the driver's side rear seat belt bracket
    • Plug in T-connector
  • 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: 5 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 10-pin tow plug, located on the driver's side behind the trim panel near the rear seat belt bracket/coil. You will have to pull back the side trim panel to access this harness.

Once installation is complete, the 4-way flat connector will be stowed beneath your vehicle, near the trailer hitch. A mounting bracket (sold separately) is recommended to keep the connector secure.

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 your vehicle runs on a multiplex wiring system, the wiring needs to be converted to be 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.

118827 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

Installation Details TK99FR Installation instructions

This Product Fits The Following Vehicles

Customer Satisfaction Score:

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - TK99FR

Average Customer Rating:  4.8 out of 5 stars   (189 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.


It’s great product for 2022 Toyota highlander. Easy to install.
Highly recommended those who want only wiring harness.


I don’t generally write reviews, good or bad, but I felt Etrailer was deserving of one. I have purchased several hitches for different vehicles over the years and have nothing but good things to say about Etrailer. Their representatives are always knowledgeable, helpful, and a pleasure to do business with. They get your purchases shipped quickly and provide accurate tracking data. For the DIYSers they have terrific installation videos for nearly every make and model. Thanks Etrailer for your service!


Everything you need for success. Thanks for being a great source for a new hitch and components.

2020 Toyota Highlander

Must watch the installation video first, and then actual installation process is very straightforward. I didn't have to use the trim remover for the 3rd trim. Outside 4pin connector is just a snap. Highly recommended! (2020 Toyota Highlander)

Toyota Highlander

Ordered this product for our 2022 Toyota Highlander. Super simple to install two connection with no need to run a power wire to the front of the vehicle. Took me longer to find that pesky 10mm socket than to install this product 10-10 recommended. (Hint) watch the install video before your order arrives makes everything go faster.


I’m grateful for a company like etrailer. Although it took longer than expected to get the part, that was out of your control due to supply chain issues created by the current administration. As far as etrailer, you’re my go to place for anything trailer. Easy to locate the part on your website. I especially like the videos you provide to show how to install on particular models and configurations. Will always go to etrailer for my trailer needs.


Install instruction had poor pictures. This leads to a little digging around behind the interior trim panel trying to determine which plug is the correct one. Had instructions been a little clearer, I would have given 5 stars.

2022 Toyota Highlander

Works exactly as stated. This is much better than cutting/splicing into the car's wiring. (like we did back in the day!)

2021 Toyota Highlander

perfect fit - very easy install with detailed instructions and video

Toyota Highlander

Installed on a 2022 Highlander. Easy install and it looks great - you can only see the hitch extension!

Toyota Highlander

Video instruction made this amazingly simple. Installed on 2021 Toyota Highlander Platinum — plug and play. Bought from etrailer because of the time they spend on customer-facing these products. I’ll support the thorough reviews and detailed instructional videos all day. Keep up the good work!


This wiring was the most simple I have ever seen! As a retired automotive technician I have wired many trailers. The connectors fit perfectly and the video instruction was superb. I took my time and maybe spent 1/2 hour to do the install. Tested circuits after installation for function on my 2020 highlander hybrid. Works perfect.


This product fit as advertised and installed exactly as the video showed. My Highlander is a 2021 Hybrid so I was worried there would be something strange or different than other Highlanders but once I found the harness connector under the bumper (exactly where the video said I would) I knew this would work. I HATE pulling plastic panels! I've broken too many clips, but this is a new car and the video showed me just where to go. The connector inside the rear panel was tied up and I elected to leave it that way to prevent rattling. Once I got it mated to the TK99FR cable it was easy to stow. Under the car, the harness connector is stowed with a plastic clip so be careful pulling the cap off (I think it was broken in the video). There was plenty of wire to reach the bracket on the hitch plate. That bracket (item #18144) was too tall to fit upright between my hitch an bumper so I mounted it as best I could so it wouldn't hang too low. I think it's important to put the head of the screw closest to the wires as the nut and threads can chafe. The 4_pole connection is a very tight fit into the bracket and I'm glad for that. I don't think it will be pushed out by mating with a trailer connector. Extremely happy with the results!

2022 Toyota Highlander

Thanks to the excellent eTrailer video had the wiring installed in my new "22 Highlander in a short amount of time. I like doing things myself and saving some money - eTrailer helps me with that!

2022 Toyota Highlander

I thought I could get away with just the trailer connector, but as I didn’t have the towing option on my 2022 Highlander, I needed this full kit. Just follow the simple instructions, and you should be able to connect everything in about 20 minutes. Great product.


Got just what I expected, very easy install just plug it in and done
E trailer makes it very simple with there install videos
Thanks e trailer !!


The T-Harness works fine - the only issue I encountered involved identifying the correct harness connector located behind the driver side panel near the third seat. There is another harness and connector nearby and identification of the correct one vs. the incorrect one could be improved...once I figured that part out there were no other issues.

Toyota Highlander

Easy installation and worked great on my Highlander. The videos were a great help and additional details for the install.

2022 Toyota Highlander

Perfect fit for 2022 Toyota Highlander and easy to install.


Installed with ease and worked the first time. There are several [online] videos out there to help with the install. But I recommend viewing the one from etrailer. The hitch works and looks fantastic.


Easy to follow instructions, still working like a champ.

2022 Toyota Highlander

Excellent product at good price. Good instructional video on how to install wiring harness. Fast delivery. Thank you etrailer.


So far so good. Wasn't hard to install by myself even though it weighs 50lbs (set it on milk cartons). Haven't used it yet but will soon. The trailer wiring was easy to install.


As advertised and video aided with inst allation!


THANKS FOR LETTING US TALK TO A REAL PERSON!! They knew their inventory and could talk us through our problems. We APPRECIATE the good service you gave us. THANK YOU!!

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