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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

Our Price: $70.78
You Save: 42%
Custom Fit Vehicle Wiring

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Shipping Weight: 0.81 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. 1-800-940-8924 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.
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  • Reviews (289)
  • Q & A (0)
  • Photos

Tekonsha Custom Fit Vehicle Wiring

  • 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

Item # TK99FR

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   (289 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 worked as advertised for a regular small trailer. I needed a 5 pin for a boat trailer which adds reverse lights to deactivate hydraulic brakes for backing up. Installed standard 7 pin round truck connector (same as my truck) for consistency-just don’t have electric brake circuit. Found reverse light circuit in rear hatch, which wasn’t ideal-especially after disassembling interior to locate 4 pin connections. Would have been awesome to disassemble just 1 location. Is the reverse circuit in the same location as the 4 pin factory wiring? Help the next guy out if you can. Thx!


Easy installation after watching the video online. Perfect fit


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.




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.



Still works! Unlike a Subaru, you need the converter. Then it’s plug and play. Easy install, both hitch and wiring.


Easy to install and good instructions

2022 Toyota Highlander

Easy installation.

2023 Toyota Highlander

Easily to hook trailers lights up to your car. No cutting or splicing your car’s electrical system. Very good directions included.

2023 Toyota Highlander

Toyota confused me! I assumed I had a trailer package installed since the rear connector under the bumper was where it is supposed to be. I was wrong! I purchased the hitch and wiring harness only to discover that my Highlander didn't have the wiring harness located inside the rear panel and my trailer lights wouldn’t work. I can’t fault since I could’ve verified my vehicle with Toyota.

etrailer pro’s:
Excellent videos on installation
Website verifies the correct item for your vehicle
Quality parts
Customer service is available and helpful
etrailer com :
My trailer was slightly bowed upon receipt and was difficult to install
I feel a better way to determine which wiring harness you need should be developed but I understand there are a LOT of vehicles out there.


Quick shipping. Wiring harness works pe rfect.


For the 2020 Toyota Highlander. Wiring harness fit perfectly and it was super easy to install. All you need is about 20 minutes of your time and some very basic hand tools. Instructions were on point.


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.



After a year of use I’ve encountered no issues….works great and would purchase again.


Exactly what I needed to activate the trailer light function. Instructions were perfect. Took 10 minutes to complete. Honestly, I was surprised it was so easy.

2010 Toyota Highlander

Quick delivery and easy install in our 2021 Toyota Highlander. Instructions didn’t point out the two 10 mm bolts you need to remove for the install but it was pretty easy to figure out. One is located above the cup holders underneath the black plug and the other is visible when you remove the cup holder.



Very happy with this purchase.


Plug and play, can't ask for more.


The hitch was perfect. I have never installed a hitch before and the videos show me exactly how to do it. I save $[XX] by doing it my self.


Installation instructions excellent. Form, fit, and function perfect.


Great product. Direction were well written and easy to understand. I will diffidently be a repeat customer.

2020 Toyota Highlander

I had a problem with the delivery system. The tracking link said it was to be here Sunday but it showed it as in transit Mon, Tues and Wed. It was originally supposed to be here on Tues but did not arrive until late Wednesday. I had an appointment to have it installed on Wednesday AM based on the original delivery date. I had to cancel that and make another appointment after it finally got here, which was several days later. Per the tracking link, the package sat in Corpus Christi for two days before it was delivered to me. This caused me problems with other commitments I had made. I realize you have not control after it has been picked up for delivery but if you had used UPS or FedEx all the way instead of USPS these problems probably would not have happened. I have a lot of stuff delivered from Amazon and they us UPS and I have never had issues with delivery times. If the reason you use USPS because it is cheaper then you are not making good business decisions.

2023 Toyota Highlander

Bought the wiring harness kit from etrailer and followed their provided instructional video. The wiring and installation went easier then expected. Everything is now installed, tested and working.
Thanks etrailer

2022 Toyota Highlander

Thank You Etrailer Technicians. Good video and explanation for installation TK99FR Wiring Harness.


This worked temporarily but threw a U0129 check engine light in my 2022 Highlander Hybrid. I reset the code and it came back in about a week. Finally removed the converter, reset, and took it to the dealer who couldn’t find anything within the car itself using their diagnostics. If anyone else has this issue, consider the converter! Not sure if mine was a dud but I ordered an OEM converter after this experience.

2021 Toyota Highlander

Was shipped with hitch. havn't installed yet. looks to be good quality

Toyota Highlander

Fit 2022 toyota highlander perfectly easy to install

Toyota Highlander

A little intimidating opening up interior panels on a brand new Toyota Highlander, but the directions were clear and it worked out well.


Works great.

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Info for this part was:

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