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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 # 118537
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Our Price: $60.13
Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Powered Converter 118537
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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. 1-636-306-4830 to order Tekonsha custom fit vehicle wiring part number 118537 or order online at Free expert support on all Tekonsha products. Guaranteed Lowest Price 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 (6)
  • Q & A (0)
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  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118537

  • 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 behind tail lights
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes ModuLite to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects directly to the 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 light: 2.1 amps per circuit
    • Tail lights: 5.6 amps per circuit
  • 1-Year limited warranty


This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located behind the driver's-side and passenger's-side tail lights. You will have to remove the tail light assemblies to access this harness.

Tail Light T Connector Diagram

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 flat connector will be stowed in an out-of-the-way location within your cargo area. 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.

118537 Tow Ready T-One Vehicle Wiring Harness

Installation Details 118537 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118537

Average Customer Rating:  5.0 out of 5 stars   (6 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.

2010 Acura TL

Easy setup plug and play

Perfect plug and play
Joseph - 10/29/2021

2010 Acura TL

Instructions were a little vague on what connector went to which plug, however it turns out only one plug would fit!

Would definitely recommend to friends looking to add to their cars.

Everything is working great. After about 4 months I had one of the tail lights on my car start to flicker then it finally died. I was worried either the harness broke the light or the light died.I went into the tail light assembly and apparently I did not fully clip in the connector and it worked its way loose. I reconnected it and secured it using some electrical tape to be sure. No issues since!Still recommend the product, was very easy and is holding up nicely.
Justin V - 05/29/2014

2009 Acura TL

Great products at an even better price! This is my second purchase from e-trailer (first was for a different vehicle), and I would definitely buy from them again.

2010 Acura TL

Install was very easy and turned out great. Thanks.

2012 Acura TL


2013 Acura TL

Simple to install on a 2013 Acura TL.


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

  • Is A Converter Required For A Vehicle Wiring Harness On A 2009 Acura TL?
    On your 2009 Acura TL a converter is indeed required so it appears the Technician was not truthful. A converter is required when vehicles have separate wiring meaning the brake light and turn signals are sent along different wires. Since trailers use combined wiring in which the brake light and turn signal are the same wire a converter is needed. For your vehicle I recommend the Tekonsha # 118537 which plugs into the existing connectors on your vehicle and uses its own power wire that...
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  • Why Does Tow Ready T-One Wiring Harness # 118537 Require a 12V Power Connection to Vehicle Battery
    There are two types of trailer wiring harnesses. There are passive types that do not have a 12V power connection; these use your car's own wiring to deliver the power to operate your trailer's lights. And there are active types that have a powered converter, such as the Tow Ready # 118537 that you have; these use the car wiring only to carry switching signals to tell the converter when to send out power for the trailer. The actual power for the trailer lights comes from the car's battery,...
    view full answer...
  • Trailer Hitch and Wiring Harness Recommendation for a 2013 Acura TL
    Since you are concerned about voiding the warranty of your TL, I recommend checking the towing section in your owners manual if you plan on installing a trailer hitch to tow a trailer. Honda states that the Acura TL was not designed for towing and doing so could void the warranty. That is something to keep in mind before installing a trailer hitch or trailer wiring harness. If you want a wiring harness because you will be carrying a hitch mounted cargo carrier with additional lights,...
    view full answer...
  • Trailer Hitch and Wiring for a 2012 Acura TL
    I believe it is the angle of the photos because both Curt hitch # C11496 and Draw-Tite trailer hitch # 24899 will have the receiver and a good portion of the cross tubing exposed below the fascia on your 2012 Acura TL. If you plan on towing with the Curt hitch then use # C45521 for the ball mount. For a 1-7/8 inch ball use # 19256 and for a 2 inch ball use # 19258. Part # F-4 is the pin and clip you need. If you will not be towing then I recommend Draw-Tite hitch # 24899 because it does...
    view full answer...
  • Recommended Hitch, Wiring Harness and Towing Accessories for 2009 Acura TL
    In terms of appearance, install procedure and weight capacity, the Draw-Tite # 24899 and the Curt # C11496 are pretty close to identical. I'd recommend the Curt # C11496 because the hitch is manufactured in the USA, and Curt does a better job on their powder coat finish, in my opinion. As for the wiring harness, I'd recommend the Tekonsha # 118537 because of its higher quality and the fact that other than the fact that you'll need to run a power wire up the positive battery terminal, the...
    view full answer...

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