bing tracking image
  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 # 118640
lowest price pledge
Retail:$120.62
Our Price: $70.16
You Save: 42%
Custom Fit Vehicle Wiring

Will this fit?

To see if this custom-fit item will work for you please tell us what vehicle you'll use it with.

Orders above $99 qualify for Free Shipping
Shipping Weight: 1.65 lbs
Quantity: 
In Stock
Tekonsha Custom Fit Vehicle Wiring - 118640
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Customer Photos

Need help with installation?
Locate installers near me
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 118640 or order online at etrailer.com. 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 (44)
  • Q & A (0)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118640

  • 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.


Features:

  • 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/cargo area
    • 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


Specs:

  • Maximum amperage:
    • Stop/turn lights: 4.2 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • 1-Year limited warranty


Installation on a Sedan

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 have to remove the plastic threshold panel and pull back the felt trunk liner to access these connection points.


Installation on a Hatchback

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 have to partially remove the plastic threshold panel, side panels, and cargo trays to access these connection points.


T-One Connection Location Points Behind Tail Lights

Once you've plugged in the T-connector, run the hot lead with the attached fuse holder to the car battery. 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 trunk/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.



118640 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Replaces 118555

Installation Details 118640 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 - 118640

Average Customer Rating:  4.8 out of 5 stars   (44 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.

- 118640
by:

I spent like 2 hours installing it, excellent product.


Comments
Absolutely
Guillermo - 04/22/2022


- 118640
by:
2014 Chevrolet Sonic

Sharing my experience installing a draw-tite hitch and wiring harness on my 2014 Chev Sonic rs. This procedure went exactly as the descriptions and videos describe from etrailer. I found only two areas that were a bit tricky - even with a trim panel tool, a couple of my trim securing plastic fasteners broke, and when going through the firewall - bit hard to maneuver around clutch pedal. Note: Replacement interior panel fasteners are plentiful and readily available. I am mechanical, but a rookie hitch installer. The hitch installation took 25 minutes with the car on ramps. The harness took approximately 1.5 hours with most of my time focused on going through firewall and doing an orderly job underhood and using caution with interior. Connecting the splices at the rear lights and routing the wire through the interior of the Sonic is very simple just as the video depicts. Great kit for the Sonic rs, and it even tucks away very nicely from an appearance standpoint!



- 118640
by:

Great product and very easy to hook up



- 118640
by:
2012 Chevrolet Volt

This is a nice product, it works great (only did short hook up so far. Yes, it will take you some time to install. I did break one of the 'green' panel holders and he local Chevy dealer doesn't stock them, so I put panel back on with out it. I also ran my 12 volt wire thru the spare tire tube. I drilled a 1/2" hole and got a .25 cent flat rubber disk from ACE. Then ran wire thru same path as fuel and rear brake lines. It was nice I could use car without 12 volt to black box so I could get the parts. Sorry, didn't take any pictures.


Comments
Made one long trip 1,200 each way with 4x8 trailer. Empty on way out but total 700-750 on way back. Hitch and lights worked great. I also got a carrier so I can haul 5 gallon gas on back and not inside car needed 1 to 2 tube, but it also works good.
Glenn - 09/20/2014


- 118640
by:
2016 Chevrolet Sonic

Works perfect, video instructions make installation simple.



- 118640
by:
2015 Chevrolet Sonic

Great wiring harness. Fairly simple and easy to install. Just make sure you have a panel tool otherwise you will break the clips that hold the interior panels in place.


Comments
It still doesn’t function at all. It’s a huge pain in the a$$ to run the power wire on my 2014 Ford Transit Connect.
Aaron - 06/28/2020


- 118640
by:

Installation was pretty simple, great quality clips/box/wires/etc., only down side is it didn't come with the 12 gauge power wire to run to the battery. Well worth the 80 bucks to not cut wires and such. If you need lights for whatever you are pulling, get this kit.


Comments
The picture shows the 12 ga wire that is needed to supply power to the unit that has to be run to the vehicle battery but the needed 12ga wire has to be procured in order for the kit to work. Misleading to me.
-- comment by: T - 02/17/2013

The 12 gauge wire is included. As always, if anyone ever finds something missing from a package, please get in contact with us and we will get it fixed. 1-800-298-8924

-- Etrailer Expert Patrick B - 2/22/2013


- 118640
by:
2014 Chevrolet Sonic

So far, easily installed and see how it does. Bought Curt brand (seems to have been discontinued) approx 3 years ago. It lost the ability to work the left signal, due to something in the "box" failing. In fairness, there were some wires touching on the trailer possibly causing damage to the box. This one seems more robust, plugged in the same, fit the same place with the box and the ground wire. Works. Now to see for how long. Trailer wires have been tied down and better protected...


Comments
It sounds like your original converter box shorted out. The typical cause of this as you mentioned is a short in the trailer wiring. Once the short is repaired, you should have smooth sailing with your new taillight converter. If theres any spot on the trailer where the wires rub against the frame, using a length of wire loom like # 39035
Wire Loom, 3/8" Diameter, 10' Long
$9.65
would be perfect for protecting the wire from abrasion. If you have wiring passing through holes in the trailer frame, using a grommet is recommended.
-- Etrailer Expert Mike L - 08/06/2018


- 118640
by:
2013 Chevrolet Sonic

I bought your products a year ago and assembly was simple and I used my hitch and wire harnesses to pull a trailer from Washington state to Oklahoma and I had no issues.



- 118640
by:

this hitch was a terrific addition to my vehicle, and was very easy to install, i installed it in under an hour by myself



- 118640
by:
2012 Chevrolet Sonic

This will be installed in a car that is overseas. 2012 chevrolet Agile,that in the UScomes out under the name Sonic... will see if all is the same.wish me luck. Is made in Argentina by Chevrolet, A division of gm south america. It will be installed by the end of march.i will let you know what happens


Comments
Unfortunately the time harness did not work, the car is a Chevrolet agile ,same as the Chevrolet sonic built I believe in usa.This one is assembled in Argentina by Chevrolet Argentina.But the wiring is different.You look at the car outside and are twins ,but the guts are different.I will be returning to USA in April 2018 but I do not believe I can have a credit for my purchase being one year past. The product is in its original package and never used
Gustavo - 03/07/2018



- 118640
by:
2016 GMC Sierra 2500

Perfect! You will need a long drill bit or sharp poker to get through the firewall. Great support videos!


Comments
Great. This product allows me to use my rebuilt light duty trailer with my vehicle.
Matthew J - 04/08/2019



- 118640
by:
2014 Chevrolet Sonic

High quality product, a little tricky running the power wire for the module to the battery on my 2014 Chevy Sonic. I did get it done and it works great.



- 118640
by:

So far so good! Installed this item about a year ago. Installation was easy and all of the parts fit properly. I use it for connecting a Harbor Freight 4x8 trailer.



- 118640
by:

I got the hitch and wire harness a few hours ago. it was right on time and we'll packaged. All the parts are there. Great service. Thank you.



- 118640
by:

I ordered a hitch and wiring kit from etrailer, it arrived today. It s exactly what I ordered and the quality of this hitch is second to none. I am extremely pleased with the quality, the super fast delivery and my overall experience with etrailer they have a customer for life.



- 118640
by:

Trailer wiring harness was a breeze to instal , works great, what more can I say?



- 118640
by:
Ford Edge

Works great and easy to install if you are patient and spend the time to properly pop the body panels loose and stuff the wires under the plastic trim. Go at least an inch or better under from the edge in the door wells or the plastic trim will sit up from the carpet making a lip. I used different wire connectors than the ones provided.



- 118640
by:

I was trapped in Nowheresville, SC without the availability to get anything other than U-Haul parts for my wife's car. Michelle helped me find the parts which I needed to get on the road home and assured me that even at 3:35PM that the shipment would get to me overnight. I cannot stress enough to friends and family WHY the only place to go for towing hardware is Etrailer.com. You can take my advice as well.



- 118640
by:

Everything plugged rite in but running power wire up to batt and making it look good was quite a prodject



- 118640
by:
2014 Chevrolet Sonic

Easy install, exactly as the videos depict with excellent detail. Item works as it should. With a manual transmission vehicle getting the black wire up through the firewall is a little harder as you have less room to operate (because of clutch pedal), but that is unavoidable.



- 118640
by:
2012 Chevrolet Sonic

Good product took a bit to feed wire to battery but it can be done ..issue i found the wire to passenger side light needs to be longer it was very tight but overall good product



- 118640
by:
2016 Chevrolet Sonic

installed trailer wireing harnass in about 40 minutes.Everything matched up with the connecters,works perfect.



- 118640
by:
2015 Chevrolet Sonic

Awesome, easy installation, got here on time. great product!!!!!


Comments
Great
Harold G - 04/03/2018



- 118640
by:
2013 Chevrolet Sonic

Although I have yet to install the hitch and wiring, it arrived faster than I expected in great condition. Great prices. Great service. I will buy from you again.


26
48
Show More Reviews

Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Will Tow Ready Trailer Wiring # 118640 Affect the Tail Light Wiring on a 2012 Chevy Sonic
    The Tow Ready wiring harness, # 118640, plugs in line with the tail light wiring on your 2012 Chevy Sonic, but it receives the power for the trailer lights from the vehicle battery. There will only be a very minimal draw on the vehicle wiring because the harness only uses the connection to the tail lights to receive the signals to send to the trailer lights. I have included a link to the installation instructions for you.
    view full answer...
  • Installation Instructions and Tips for Trailer Wiring Harness on a 2014 Chevy Sonic
    No videos yet showing installation of trailer wiring harnesses on a 2014 Chevy Sonic but I have linked the instructions for # 118640. The only part that would be tricky is routing the power wire to the vehicle battery. And even that is not difficult, it just takes a little longer. I have included a link to a help article with tips on routing the power wire for you.
    view full answer...
  • Install Time of the T-One Vehicle Wiring Harness Part # 118640 On a 2015 Chevrolet Sonic
    Unfortunately, we do not have an average install time for the T-One Vehicle Wiring Harness part # 118640 which is a fit for your 2015 Chevrolet Sonic Sedan. However, we do have an install video on a similar version which you can then use to gauge how long the install will take you. I have also attached the printed instructions for you as well. The process is not difficult but it will take a bit of time out of your day. The amount of time will vary depending on skill level which is why it...
    view full answer...
  • Trailer Wiring Harness Installation on 2016 Chevrolet Sonic
    Yes, on the wiring harness # 118640 you will need the black 12-volt power wire coming from the converter box to be connected to the battery on your 2016 Chevrolet Sonic. The converter box is necessary to protect the wiring of your Sonic and also your tail light circuits do not have enough capacity to power the LED lights on the trailer. The black wire supplies the power to the trailer lights and uses the signals coming from the Sonic's lights to determine which circuits to supply power...
    view full answer...
  • Needing Trailer Wiring Harness to Operate Reverse Lamps on Trailer
    The Tow Ready T-One Vehicle Wiring Harness you referred to, part # 118640 will feed the trailer running lamps, brake lamps and right and left directional signals, but not reverse lamps. We do not have a plug and play wiring harness option that would provide a 5-pole, but you could hardwire one using part # 119177KIT. You would use the tester included in the kit to test the wires feeding the factory taillight assemblies to locate which wire carries the right turn, left turn, brake lamp,...
    view full answer...
  • Does Trailer Wiring Harness Come with the Curt Trailer Hitch for a 2013 Chevy Sonic RS
    The trailer wiring harness is not included with Curt trailer hitch # C11398 for your 2013 Chevy Sonic RS. The reason is because not everyone who installs a hitch is using it for towing or accessories that have lights. By making it separate the hitch price can be lower. To add a trailer wiring harness you can use # 118640. This will add a 4-Way flat connector to the rear of the vehicle. I have linked a video showing an example installation for you.
    view full answer...
  • Parts Needed to Tow Small Trailer with 2012 Chevy Sonic Hatchback
    We only have Class I hitches available for your vehicle which have the 2,000 lb total capacity and 200 lb tongue weight capacity. If you are sure your trailer is under that weight and your vehicle's owners manual also reflects at least the same capacities you would be good to go with a hitch like the # 24878 that you mentioned. For trailer wiring you'd then want the part # 118640 which is a confirmed fit as well. For a ball mount you'd need the part # 3590, and for a ball # 19256.
    view full answer...
  • Trailer Hitch Recommendation for a 2012 Chevy Sonic Hatchback
    For your 2012 Chevy Sonic hatchback you can use Draw-Tite trailer hitch # 24878. I have included a link to the installation instructions for you to view. The recommended ball mount is # 3590. If you plan to tow, first check the vehicle owners manual for information on towing. For a 1-7/8 inch ball use # 19256 and for a 2 inch ball use # 19258. For trailer wiring use # 118640.
    view full answer...
  • Trailer Hitch Recommendation for a 2013 Chevy Sonic RS
    I checked with Draw-Tite and they do list trailer hitch # 24878 as a fit for all models of the 2013 Chevy Sonic hatchback so that would include an RS. I have included a link to the installation instructions for you to view. If you plan on doing some light towing first consult your owners manual. For a ball mount use # 3590. For a 1-7/8 inch ball use # 19256 and for a 2 inch use # 19258. For trailer wiring use # 118640.
    view full answer...
  • 2015 Chevy Sonic Hatchback Trailer Hitch and Wiring Recommendation
    For your 2015 Chevy Sonic the Draw Tite Hitch part # 24878 has been confirmed as a fit and will work well for light towing as long as you stay under the hitch's towing capacity of 200 lbs tongue weight and 2,000 lbs total trailer weight and the towing capacities for the vehicle listed in the owners manual. I attached an install video for you to check out as well. For trailer wiring you would then want the part # 118640, for a ball mount # 3590, 1-7/8 inch ball # 19256, and 2 inch ball # 19258.
    view full answer...
  • Trailer Hitch and Wiring for a 2013 Chevy Sonic RS to Tow a Motorcycle
    In order to transport a motorcycle using your 2013 Chevy Sonic RS it will have to be towed on a trailer. The problem is that the bike is too heavy to carry it on a hitch mounted carrier. They do make small trailers designed for motorcycles so you won't need a huge trailer. For a trailer hitch I recommend Draw-Tite model # 24878. The recommended ball mount is # 3590. For a 1-7/8 inch ball I recommend # 19256 and for a 2 inch ball I recommend # 19258. For trailer wiring I recommend # 118640...
    view full answer...
  • Trailer Hitch Recommendation for a 2012 Chevy Sonic Hatchback
    For a hitch for your 2012 Chevy Sonic hatchback I would recommend the Draw Tite Hitch part # 24878 as it is the most popular hitch we offer confirmed to fit your vehicle. This hitch has a 200 lb tongue weight and 2,000 lb total trailer weight capacity so you will need to be sure the trailer weighs less than that when totally loaded. Also, you will need to check the owners manual of your vehicle to determine what Chevy says is your towing capacities. The lower of the two sets of capacities...
    view full answer...
  • Trailer Hitch Recommendation for a 2013 Chevy Sonic Hatchback
    We do have trailer hitches for the 2013 Chevy Sonic hatchback but # 24876 will not fit. The equivalent hitch that will fit your 2013 is Draw-Tite hitch # 24878. I have included a link to the installation instructions for you. If you plan on doing some towing the correct ball mount is # 3590 and the correct pin and clip is # PC2. For a 1-7/8 inch ball use # 19256 and for a 2 inch use # 19258. For trailer wiring use # 118640. I have linked instructions for the wiring as well.
    view full answer...
  • Is Drilling Required to Install a Curt Trailer Hitch on a 2013 Chevrolet Sonic LT Hatchback
    There is no drilling required to install Curt trailer hitch # C11258 on your 2013 Chevy Sonic. Installation is estimated between 1/2 hour and 1-1/2 hours depending on your level of ability and whether or not you have someone to help. You will not have to remove or trim anything either. I have included a link to the installation instructions for you. If you will be using the hitch for hitch mount accessories such as a bike rack or cargo carrier you will need to make sure that the chosen...
    view full answer...
  • Can a Trailer Hitch be Installed on a 2015 Chevy Sonic Hatchback with Upgraded Exhaust
    Trailer hitches are designed for and tested on stock vehicles so there isn't an easy way to determine if any of them would be compatible with the aftermarket exhaust. However, if the exhaust is professionally installed they would be able to work around any clearance issues with the hitch so I would have the hitch installed first. If you plan on doing any towing I recommend Draw-Tite trailer hitch # 24878. The recommended ball mount is # 3590. Then for a 1-7/8 inch ball I recommend # 19256...
    view full answer...
  • Recommended Tow Bar Wiring For 2016 Chevrolet Sonic Being Flat Towed
    I have another option for you, but the Tekonsha T-One Vehicle Wiring harness # 118640 you purchased for your 2016 Chevrolet Sonic is for connecting to a trailer and will not power the lights when you are flat towing. Instead you will need the Roadmaster Tail Light Wiring Kit with Bulbs # RM-155 which will allow your RV to power the lights of your Sonic while it is being flat towed. If you RV has a 7-way connector you will also need 7-way to 4-way adapter # PK12716. You will not be able...
    view full answer...
  • Trailer Hitch and WIring Recommendations for a 2014 Chevy Sonic Sedan
    Yes, Curt trailer hitch # C11240 will fit your 2014 Chevy Sonic sedan. I have linked a video to the right showing installation of the trailer hitch for you. If you plan on using the hitch for a bike rack or cargo carrier please make sure that the accessory is rated for a Class I trailer hitch. Also, with bike racks or cargo carriers Curt requires the use of stabilization strap # 18050 when using those items or any non-trailer load in the hitch. If you want to tow you will want to consult...
    view full answer...
  • Recommended Trailer Hitch For 2012 Chevrolet Sonic
    There were two models of the Chevrolet Sonic lt in 2012. One is a 4-door sedan and the other model is a 5-door hatchback. If you have a 4-door sedan then the trailer hitch I recommend is part # 24876. This is a Class l trailer hitch and it has a 1-1/4 inch receiver opening. For a 5-door hatchback I recommend part # 24878. This is also a Class l hitch with a 1-1/4 inch receiver opening. I recommend the Draw-Tite trailer hitches because a stabilizing strap like part # 18050 is not required...
    view full answer...




  • Why etrailer.com?

    At etrailer.com we guarantee:
  • Highest quality custom fit vehicle wiring for the best price.

    Our Lowest Price Pledge ensures you will never overpay for the parts you need.
  • Real product know-how.

    We make sure that the products we sell are what we say they are, and that they work the way they are supposed to work. Get real advice from a real person who has the knowledge and expertise needed to solve your problem.
  • Most detailed, accurate custom fit vehicle wiring information available.

    Because we take providing accurate product information seriously, we take our own detailed product photos, demo videos and installation videos, as well as verify measurements, instructions, and vehicle fit information.
  • Installations, made easy.

    We love helping people and have the most highly-trained customer service, hands-on experience, step by step videos and installation instructions.
  • Fast shipping.

    Your order is automatically routed to get out of our warehouse and to your door as quickly as possible. Receive free shipping on orders over $99.
  • Personalized service for life.

    We provide one-on-one, personalized service from the ordering process through the life of your product.
  • Trusted since 1946.

    We've been serving customers since our parts store first opened in 1946 and continue to be recognized by our customers, our vendors and third parties for exceptional service.
  • Returns Policy

    Need to return an item? No problem. Please read our Returns Policy for more information.

Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Brent H
Test Fit:
Brent H
Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video Edited:
Joshua S
Employee Jacob T
Video Edited:
Jacob T
Employee Laura H
Written by:
Laura H
Employee Rachael H
Updated by:
Rachael H
Employee Wilson B
Updated by:
Wilson B
Employee Alexander C
Updated by:
Alexander C
Employee Isabelle B
Updated by:
Isabelle B
Employee Hayden R
Video by:
Hayden R

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time.