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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 # 118718
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Custom Fit Vehicle Wiring

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118718 - 4 Flat Tekonsha Custom Fit Vehicle Wiring
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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. Call 800-298-1624 to order Tekonsha custom fit vehicle wiring part number 118718 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.
  • All Info
  • Reviews (4)
  • Q & A (0)
  • Videos (1)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118718

  • 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
    • Connect hot lead to car battery
  • Includes ModuLite to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects directly 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 wiring harness, which is located in your rear cargo area on both the driver's side and the passenger's side. You will have to remove the rear threshold panel, cargo trays, and interior paneling 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 flat connector will be stowed in your rear 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. 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.

118718 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

Installation Details 118718 Installation instructions

This Product Fits The Following Vehicles

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 - 118718 Review

Today we're going to be taking a look at T1 Vehicle Wiring Harness with a 4 pole flat trailer connector. This product fits certain years of the Mazda CX-3. To see or double check if this is a fit for your vehicle, you can use the Vehicle Fit Guide located at This unit's going to provide a four way flat trailer connector at the back of your vehicle to power your trailer's signal lights. It is compatible with 5 pole, 6 pole, and 7 pole adapters. Adapters are sold separately, and it's going to come with a dust cap for the four way flat connector.

That way you can cover up the connection points when you're plug's not being used. The black box on the unit, this is the included ModuLite. This is designed to ensure that your vehicle's wiring matches out of your trailers. The power module connects directly to the vehicle battery through the wiring to avoid overloading your vehicle's electrical system. This is designed to connect quickly and easily. All you need to do is locate the connection points in the rear cargo area and plug in your T connectors.

You're going to have one set that goes to the driver's side. The other set goes to the passenger side of the vehicle. These plugs are going to be custom fit. They're going to match perfectly with the ports on the vehicle and they're going to snap lock together for a nice tight secure fit. Once you have those connected, you'll need to make a ground connection. That's going to be your white wire with a ring terminal attached to it.

You want to get that grounded to a nice clean metal location. You can do that using the included ground in screw or you can make the ground by mounting that to an already existing grounding point in the vehicle frame or sheet metal. Then you'll need to mount your converter box. Your converter box is going to mount using the double-sided adhesive foam tape that's provided with the kit. You just want to be sure to get that mounted to a nice clean out of the way location. Then you'll need to run the hot lead to the vehicle battery.

The hot lead is this black wire here. This is going to get connected to the bundle of black wire with one of the included butt connectors. The other end of the bundle runs to the vehicle battery. It gets another butt connector attached to it and connects to one half of the fuse holder. The other half of your fuse holder gets a ring terminal attached to it and connects to the positive post on the vehicle battery. It also comes with your 15 amp fuse. It goes directly into the fuse holder and it's got the cap that goes over it to keep that safe and protected. Then you can secure any excess or slack in your wiring with the included cable ties. Once your installation's complete, the four way connectors are going to be stowed in your rear cargo area. It is recommended that you use a small amount of dielectric grease on all of your electrical connections, like the plugs on the vehicle, and the 4 pole connector. That's going to help prevent corrosion to the connection points. It is sold separately and can be found here at When it comes to the maximum amperage for the stop and turn lights, you're looking at 5 amps per circuit. For the taillights, we're looking at 7.5 amps per circuit. That's going to do it for today's look at the T1 vehicle wiring harness with a 4 pole flat trailer connector.

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118718

Average Customer Rating:  4.8 out of 5 stars   (4 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.

- 118718

So far so good. Only thing is in a Mazda CX3 there isn’t a spot on the firewall to slip a power wire through without drilling a hole so I painstakingly followed the brake lines and zip tied it from the battery to the trunk. Also I wish the wires that hook up to the drivers side rear lights were about six inches longer so I had more options to secure the box.

- 118718

My second order from etrailer and found everything to come as promised. Quality hitch, on time. Great support with installation videos too.

- 118718

Feels high quality and does its job

- 118718
2019 Mazda CX-3


Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Hitch and Wiring Recommendation for Towing a Trailer with a 2019 Mazda CX3
    The best hitch option for your 2019 Mazda CX3 is Curt hitch part # C11418. Both the Draw-Tite and Curt option for the Mazda are Class I options and can handle up to 200 lbs of tongue weight. I recommend the Curt hitch because installation takes less time compared to the Draw-Tite option. The Curt hitch hardware is easier to access when it is time to torque down the bolts during installation. I have attached an installation video of the Curt hitch on a 2017 Mazda CX-3. The Curt option...
    view full answer...
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  • Trailer Hitch Fit Recommendation for a 2017 Mazda CX-3
    Officially we have to recommend that you always stay with the recommendation of the manufacturer on towing as they are who the warranty of the vehicle is with and they are who would have tested the vehicle for towing. That being said we realize that a lot of people ignore their owners manual and tow with vehicles that aren't designed for it and allegedly do not have any problems. So our hitch manufacturers make hitches for these vehicles as there is a demand for them but it's a situation...
    view full answer...
  • Is 12V Power Connection Required for Tekonsha T-One 4-Pole Wiring Harness 118718 to Function
    Yes, the Tekonsha T-One 4-Pole Wiring Harness # 118718 will work fine to power LED lights on a trailer or accessory carrier used with your 2019 Mazda CX-3 but it does require the 12V power wire connection in order to function. The plug-in connectors will take in the car's lighting signals which essentially serve as switches to tell the converter to send lighting power out to the 4-pole. The actual current to operate the lights comes from the power wire that you route up to the battery;...
    view full answer...
  • Can Tongue Weight for Trailer Hitch on 2019 Mazda CX-3 Be Exceeded
    We cannot recommend you exceed the 200 lb tongue weight of the hitch that fits your 2019 Mazda CX-3, the Draw-Tite Trailer Hitch Receiver # 24933. It is not designed to have that much weight so there's no telling if the structure can be impacted. This is the only available capacity for your CX-3, so if you want to haul your dirt bike with this vehicle the best option really is a trailer. To do that you will need the hitch, along with T-One Vehicle Wiring Harness # 118718, Draw-Tite Drawbar...
    view full answer...
  • Recommended Ball Mount for 2018 Mazda CX-3 that Has Draw Tite Hitch
    With Class I hitches like the Draw Tite part # 24933 that you referenced you have to use the ball mount that the hitch manufacturer requires which in this case is the Draw Tite part # 3593. Then for hitch balls you'd want the part # 19258 for a 2 inch ball or part # 19256 for a 1-7/8 inch ball. You'll want trailer wiring too which for that the Tekonsha kit part # 118718 is the kit I recommend as it installs easily and has a very reliable converter box.
    view full answer...

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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Adam R
Expert Research:
Adam R
Employee Cole B
Installed by:
Cole B
Employee Chris R
Video Edited:
Chris R
Employee Wilson B
Updated by:
Wilson B
Employee Isabelle B
Updated by:
Isabelle B
Employee Alexander C
Written by:
Alexander C

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