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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 # 118581
Our Price: $61.17
You Save: 35%
Custom Fit Vehicle Wiring

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Tekonsha Custom Fit Custom Fit Vehicle Wiring - 118581
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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 118581 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 (11)
  • Q & A (0)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118581

  • 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 trunk
    • 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 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: 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 inside your trunk, behind the tail lights on both the driver's side and passenger's side. You will need to remove some interior trim or carpeting to access the 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 an out-of-the-way location within 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.

118581 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Installation Details 118581 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Satisfaction Score:

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118581

Average Customer Rating:  5.0 out of 5 stars   (11 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.


Removing the vehicle interior was the timely part of the install. Once that was done, wiring was very easy. However, vehicle designers should have allowed for a power tap under the dashboard for accessories. I did dress the wiring before reinstalling the interior panels. For this vehicle, hitch installation was made easier by removing the muffler from the vehicle and using a uni-bit to enlarge the access holes used for the install of the backing plates and bolts.

2012 Subaru Impreza

Fit the existing plugs on my 2012 Subaru Impreza. The time consuming part was placing the wire to the battery. Tucked it in along the interior out of sight.

2015 Subaru WRX

I checked out the connectors on the tail lights and they are the same as previous years. Compared the service manual wiring diagrams to the pictures on the website and they corresponded to the same pinouts. They were the same. So the TowReady #118581 turned out to be plug-n-play afterall for my 2015 WRX Limited. Once I installed the kit, I tested it with a trailer light tester and everything worked as it should. I ran out of time or I would've hooked it up to the trailer tail lights for a true test. I'm installing a set of LED tail lights on the trailer that only draw 444mA (0.444A) along with a Curt C56196 to make it work with separate amber signals and stop lights. Other than routing the wiring to the battery (which I did through the interior of the car and through the firewall (which was a pain) but it has a clean factory finish that I wanted over splicing into the factory wiring harness.

2015 Subaru Impreza

Amazing product, just plug and play.
recommend this to anyone who wants to save some time.
Thanks etrailer.


Worked great after installation. No p roblems

Been working fine, no problems.
Charles F - 06/27/2016


The kit was very easy to install and the instructions were clear. This was my first time installing wiring of any kind in a car and it took me under 30 min.

2015 Subaru Impreza

Great hardware and wiring ... definitely helps to be able to putt a trailer with my Impreza!


2016 Subaru Impreza

Great customer service!

by: 02/09/2022
2012 Subaru Outback Wagon

by: 08/31/2021


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

  • Trailer Wiring Harness Recommendation for 2013 Subaru Impreza
    Yes, the T-One trailer wiring harness part # 118581 is a confirmed fit for your 2013 Subaru Impreza sedan and would be a great fit. We recommend this brand the highest as it tends to be the most reliable over time.
    view full answer...
  • Custom Fit Vehicle Wiring on a 2016 Subaru Impreza Hatchback
    I can agree with you that running the power wire can be time consuming. It does make it easier if you can get the back of the vehicle on ramps. The hardest part is routing the power wire over the rear axle and staying away from anything hot or moving. Once you get past the axle you can run the wire along some factory hard lines or in between a plastic panel and the body to the front. All of the wiring kits for the 2016 Subaru Impreza require a power wire be ran to the battery. The power...
    view full answer...
  • Trailer Wiring Recommendation for a 2014 Subaru Impreza Hatchback
    For your 2014 Subaru Impreza hatchback you would have to use a hardwire harness for trailer wiring like the part # 119179KIT. The plug and play harness like the # 118581 will only fit the sedans.
    view full answer...
  • How to Troubleshoot Trailer Wiring Converter Box for Short
    What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the # PTW2993 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test the output side of the box to see if the current is making it through the converter. If not then the problem is that the converter box has shorted itself out and would need to be replaced. Before you replace it you will want to inspect...
    view full answer...
  • Troubleshooting Non-Functioning Headlights After Wiring Harness Installation on 2015 Subaru Impreza
    We offer different wiring harnesses for the 2015 Subaru Impreza depending on whether it is the sedan or the 5-door wagon. The sedan uses part # 118581 and the 5-door wagon use the item you referenced, part # 118573. Both install in the same way, by plugging in at the taillight connectors behind the car's rear lights. The same circuit handles both the car headlights and the taillights. Odds are that either there is now a blown headlight fuse that needs to be replaced or that there is a...
    view full answer...
  • Recommended Trailer Hitch For 2017 Subaru Impreza 4 Door Sedan
    For a 2017 Subaru Impreza 4 door, I recommend the Draw-Tite Sportframe Trailer Hitch Receiver Class I - 1-1/4" # 24960. This is a confirmed fit for that vehicle. It is a bolt on installation with a sturdy, square design. It has a black powder coat finish covering an e-coat base for superior rust protection. If you will be towing with this hitch, I recommend the Sportframe Drawbar 4" Rise 2000 lb kit # 3594. This comes with the pin and clip, but you will need a hitch ball. I recommend...
    view full answer...
  • Trailer Hitch Recommendation for 2013 Subaru Impreza Sedan
    The trailer hitch you want for your 2013 Subaru Impreza four door is the EcoHitch part # 306-X7241. This hitch has a 2 inch opening which means that it would allow you to carry a bike rack with more than 2 bikes loaded since you mentioned wanting to carry a 3 bike rack. For trailer wiring I'd then recommend the Tekonsha kit part # 118581 which will install without splicing and has our most reliable converter box. Since you plan on doing some towing you might be interested in etrailer...
    view full answer...
  • Availability of Trailer Hitch for 2014 Subaru Impreza Sedan
    We have several hitches available for the 2014 Subaru Impreza sedan, depending on the model. If you have the WRX or WRX STi models you will want Curt hitch # C11317. If you plan on doing some towing, you will want ball mount # C45521, 2" hitch ball # A-82, 1-7/8" hitch ball # A-80, and wiring harness # 118581. Pin and clip are included. If you plan to do some light towing you will want ball mount # C45521, 2" hitch ball # A-82, 1-7/8" hitch ball # A-80, and wiring harness # 118581. Pin...
    view full answer...
  • Can a 2014 Subaru Impreza Carry a Motorcycle Carrier over 350 lbs Tongue Weight?
    For your 2014 Subaru Impreza, we don't have any trailer hitch rated for over 350 lbs tongue weight. I don't recommend having a trailer hitch made for your application because the vehicle is not rated for that kind of weight. Your best option to transport your motorcycle is to use a trailer hitch and trailer. I recommend the EcoHitch Invisi Trailer Hitch Receiver - Custom Fit - Class III - 2" # 306-X7241 if you have the sedan or # 306-X7211 if you have the wagon with single exhaust. ...
    view full answer...
  • Best Way of Carrying Motorcycle on 2015 Subaru Impreza
    The only hitches available for a 2015 Subaru Impreza are a Class I, which would lack the tongue weight capacity to handle the weight of your bike plus a hitch mounted carrier. Typically this happens when it's determined that the under body structure of the vehicle isn't capable of handling weight in excess of 200 lbs. Your best bet would be to install a hitch and use a small trailer. For the 5 door wagon with a single exhaust, I'd recommend the Curt # C11286 and the Tekonsha # 118573 wiring...
    view full answer...

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