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 # 118790
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Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Custom Fit 118790
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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 118790 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.
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  • Reviews (34951)
  • Q & A (25)
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Tekonsha Custom Fit Vehicle Wiring - 118790

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • Tekonsha
  • Powered Converter

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 point in rear cargo area
    • Plug in T-connector
  • 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: 5 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • 1-Year limited warranty


Installation

This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located inside your trunk, behind the rear interior trim panel on the driver's side of the rear cargo area. You will need to remove access panels, threshold, trunk floor panels, and trays to access the harness. Once you've plugged in the T-connector, pull back the interior trim panel on the driver's side and locate the ground stud. Loosen the bolt, place the screw eyelet on the stud and re-tighten the bolt.


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. 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.



118790 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Installation Details 118790 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 - 118790

Average Customer Rating:  4.8 out of 5 stars   (34928 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.

- 118790
by:

Easy install. Bought this with the Curt Class III hitch. All components match up and install without a struggle. The Tekonskha Custom Fit harness incorporates turn signals, running lights and brake lights.



- 118790
by:
Subaru

I purchased this for my 2019 Subaru Ascent along with a Drawtite hitch 76253 and a brake controller with a dash mounted control knob so that the actual controller is hidden near the steering wheel shaft hidden under the dash. All three items were installed and we enjoyed a great summer of RV trailer camping in the summer of 2019.


Comments
I had an RV service professional install it because I am too claustrophobic under my Ascent and I am very happy that it is hidden behind with only the control button visible and it works great!
John - 05/01/2021


- 118790
by:

One year and still going strong. Would definitely recommend the harness and eTrailer



- 118790
by:

the wiring harness is very good and installation was good. never have gotten the actual hitch fitted up yet though.



- 118790
by:

I was impressed with the installation service, the finished appearance and the price.



- 118790
by:

Extremely easy to install. Good instruc tions.



- 118790
by:

very easy to install, and works as inte nded.



- 118790
by:

Received order in timely fashion as usual from etrailer. Product worked as advertised. I have been a customer for 15 years or more and consider etrailer service and products the industry best.



- 118790
by:

I ordered this item along with the trailer hitch and a bracket. The item was packaged great and arrived in timely fashion. The company was fantastic to work with and service was outstanding. Finally, the online tutorials on the etrailer website made putting these items in place easy. I am 150% satisfied with everything this company has done!



- 118790
by:

Arrived quickly with my hitch and, after watching the video (A must!), it installed very easily and quickly with no surprises! This can easily be installed with just the tool needed for attaching the ground wire.


Comments
Great! Required some voltmeter testing to match the right wire to the right harness wire though.
Travis P - 03/30/2020



- 118790
by:

Everything couldn't have been better. From the installation videos, to the great and timely service, E-Trailer was great and I will be working with them in the future.



- 118790
by:

The hitch came quickly and installed easily. I have a 2020 Subaru Ascent the hitch was listed for a 2019, and fit the 2020 perfectly. Very happy with the result. Need to add the quick release clips for the body panel cover so that the cover can be removed quickly to expose the hitch. Videos and instructions were very helpful.



- 118790
by:

Super easy to install. The install video walks you through each step, and there were no surprises when I installed it on my vehicle. Really like the black box that protects the vehicles wiring in case I rent a trailer with a short in it.



- 118790
by:
2019 Subaru Ascent



- 118790
by:

Very easy to install. The only difficulty is actually getting to the place where the harness is to be placed. Instructions are easy to follow and, with a little care, the system can be installed with no issues.



- 118790
by:



- 118790
by:

Easy to install. Lots of videos and helpful suggestions on the internet for this type of installation.



- 118790
by:

Great product at good price. Easy to install and has been working with no issues



- 118790
by:

Works as advertised



- 118790
by:



- 118790
by:

Tekonsha prouducts always fit,work as expected,and have clear and direct instructions



- 118790
by:



- 118790
by:
2020 Subaru Ascent

Order was filled and delivered quickly and efficiently. Great customer service.



- 118790
by:



- 118790
by:
2020 Subaru Ascent

Super easy to install and very clean looking,have not used it yet but everything tested good on the testers.


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Show More Reviews

Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Can 2021 Subaru Ascent With Curt Trailer Hitch Use Weight Distribution
    That's a good question, and the short answer is yes, you can use a weight distribution hitch with the Curt hitch that fits your 2021 Subaru Ascent: - Curt Trailer Hitch Receiver # C25VR I took a look at the owner's manual for the 2021 Subaru Ascent, and it is referring to the factory hitch in regards to not using weight distribution. The reason is, that hitch is not rated for use with a weight distribution system, but the Curt # C25VR rated for use, which is why you can use it for...
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  • Parts Needed to Add 7-Way and Brake Controller to 2019 Subaru Ascent Without Tow Package
    There are just a couple parts needed in order for you to add a 7-way and brake controller to your 2019 Subaru Ascent. Because you already have the required 4-way 118790, to add a wireless brake controller, which I strongly recommend due to how very easy they are to use, you'll just need the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation # ETBC7L. This will allow you to use the Curt Echo Wireless Trailer Brake Controller # C51180. The Curt Echo will simply plug into...
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  • Recommended Hidden Hitch and Wiring For 2020 Subaru Ascent
    The Curt Trailer Hitch Receiver 2" part # C25VR is a fit for the 2020 Subaru Ascent. The Curt hitch is hidden behind the removable fascia panel at the rear the Subaru. When the hitch is not in use the panel can be replaced for a completely hidden clean OEM look. I have attached a photo for your reference. If you plan on towing a trailer you will need wiring. For that I recommend T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part # 118790. The Tekonsha wiring is more...
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    Image 1 for
  • What is the Difference Between the Draw-Tite 76253 and Curt C25VR for 2020 Subaru Ascent
    There are some slight differences between the Draw-Tite # 76253 and the Curt # C25VR, but it's mostly down to the quality of the powder coat on the two hitches. The powder coating on the Curt hitches is traditionally applied a bit thicker and is a better quality, in my opinion. This is going to translate to less dings and scratches and generally means that the hitch is going to be less susceptible to corrosion over the long term, so I do recommend going with the Curt # C25VR hitch for your...
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  • Comparing Draw-Tite and Curt Trailer Hitches for 2019 Subaru Ascent Touring
    The benefits of the Draw-Tite Trailer Hitch # 76253 that fits your 2019 Subaru Ascent Touring are that it has a concealed crosstube and also that it has a 750 lb tongue weight, which is the highest capacity tongue weight for any hitch that fits your vehicle. That said, the tongue weight will not come into play when you are using your bike rack and it is unlikely to be a factor for a tent trailer. The Curt Trailer Hitch # C13400, which will also fit a Touring model of '19 Ascent, has...
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  • 2019 Subaru Ascent 4-Way and Brake Controller Install Kit
    Your 2019 Subaru Ascent should have came with a 7-way installed at the rear of it if it came with the factory towing package. Since you are having a hitch installed currently and looking at wiring you most likely do not have the towing package and would need to install the correct wiring. You have to start with a 4-way for this like the # 118790 as this will be the base for the 7-way conversion needed to install and use the brake controller. Since normally this 4-way kit stores in the rear...
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  • Does The Impact Structure/Bumper Beam Need To Be Removed To Install Hitch on 2019 Subaru Ascent
    Yes, both the Draw-Tite hitch part # 76253 and EcoHitch part # 306-X7381 require removal of the impact structure. Since both the Draw-Tite and EcoHitch are concealed cross tube designs the impact structure must be removed to make room for the cross member of the hitch. Curt hitch part # C13400 for the 2019 Subaru Ascent does not require removal of the impact structure because it is installed below the bumper. I recommend the Draw-Tite hitch part # 76253 because the cost is less expensive...
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  • Can the Draw-Tite # 76253 Trailer Hitch be Used to Tow a Pop Up Camper with a 2019 Subaru Ascent
    Yes! The Draw-Tite Max-Frame Trailer Hitch Receiver # 76253 is an excellent option for towing a pop up camper with your 2019 Subaru Ascent. You will need some additional items to tow your pop up camper. I took a look at the online version of your owner's manual and it states that your Ascent is only capable of towing a trailer up to 1,000 lbs if it doesn't have brakes. If your Ascent has the air-cooled continuously variable transmission fluid cooler then you can tow up to 5,000 lbs...
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    Image 1 for
  • Comparing the Best Hitches for the 2020 Subaru Ascent
    The biggest difference between the Draw-Tite Max-Frame Trailer Hitch Receiver - Custom Fit - Class III - 2" part # 76253 and the Curt Trailer Hitch Receiver - Custom Fit - Class III - 2" part # C13400 is going to be how they look when installed. The DrawTite has a look extremely similar to the factory style hitch. It sits behind the factory hitch cover and is not visible at all when not in use. The Curt will sit below the rear bumper cover and has an exposed cross tube and receiver tube...
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    Image 1 for Image 2 for
  • Brake Controller Recommendation and Install for 2020 Subaru Ascent
    I'd give the Tekonsha # 90195 the edge for ease of use. The full LCD display provides the status of your braking system at a glance, while the # 331-EBRH-ACCV2 Redarc Tow Pro Elite uses colored LED's to indicate problems. The display of the P3 is much more intuitive and user-friendly. However, some folks absolutely hate the appearance of a typical brake controller and want it to be as hidden as possible. If you fall into that camp, the Redarc Tow Pro Elite might be a better choice. Performance...
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    Image 1 for
  • Hitch Recommendation for 2020 Subaru Ascent that Fits Behind Bumper Panel
    We do have hitches that fit behind the bumper of your 2020 Subaru Ascent. The one I recommend is the Draw Tite part # 76253 as it fits behind your bumper like you want and is also priced the best. I attached a picture of what it looks like installed as well as an install video for you to check out too. For trailer wiring then the kit I recommend is the # 118790 which installs very easily and also comes with a very reliable converter box so it will last a long time!
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  • Trailer Hitch Recommendation for 2019 Subaru Ascent
    Yes, for your 2019 Subaru Ascent the Draw Tite hitch part # 76253 is a confirmed fit and would work well for you. It is a 2 inch hitch which is the most popular size and has plenty of towing capacity at 5,00 lb trailer weight. For trailer wiring you'd then want the part # 118790.
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  • Recommended Hitch For Carrying Bike Rack on 2020 Subaru Ascent
    I'd recommend going with a concealed option like the # 76253 from Draw-Tite. When the hitch isn't needed, it'll be completely concealed behind the center panel in the rear bumper cover. Many folks don't care for the appearance of a trailer hitch such as the Curt # C13400 which will be fully visible below the rear bumper. If there's a chance you might use the hitch for towing purposes some time in the future, you'd need a few other items to complete your towing system. For a trailer wiring...
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  • Installing Redarc Tow Pro Elite 331-EBRH-ACCV2 Brake Controller on 2020 Subaru Ascent
    If your 2020 Subaru Ascent has the factory tow package with the factory installed 7-way trailer connector, it will have the factory brake controller connector located above the driver's side kick panel forward of the hood latch as shown in the provided photo. The wiring harness is part # 3062-P. If your Ascent does NOT have the factory 7-way, you'll need to install a # 118790 wiring harness to provide one. You'd then use the # ETBC7 brake controller wiring kit to install controller.
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  • Trailer Hitch and Wiring for 2019 Subaru Ascent and Should Weight Distribution be Used
    If the manufacturer of the vehicles states that you can't use a weight distribution system then you should not use it. They designed the frame of the vehicle and are the authority on whether or not it could handle the additional stress of a the system. I'd recommend finding a trailer that is under the towing capacity of your 2019 Subaru Ascent and then installing the Draw Tite hitch part # 76253 you referenced which would give you a 2 inch hitch that fits behind the rear bumper panel. I...
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  • Does Draw Tite Trailer Hitch for 2019 Subaru Ascent Have Capacity for Towing
    I certainly understand the concerns you mentioned for the Draw Tite hitch # 76253 which fits your 2019 Subaru Ascent but Draw Tite rigorously tested the capacity of this hitch and found it has a towing capacity of 5,000 lbs and a tongue weight capacity of 750 lbs. Draw Tite is normally very conservative with their capacity figures as well and tends to err on the side of caution always in this regard. As long as you plan to tow under the capacity of this hitch and your vehicle you will be...
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  • Trailer Wiring Recommended for 2019 Subaru Ascent to Use Curt Echo Brake Controller
    We can get your 2019 Subaru Ascent set up with the exact trailer wiring you will need so you can install and use the Curt Echo Wireless Trailer Brake Controller # C51180. The first thing you will need is a 4-way, and the best option for that is from Tekonsha, as they make the most reliable trailer wiring harnesses and because it has the highest amp rating which means it gives you the best prevention against potential shorts. The correct harness for your 2019 Ascent is the following: -...
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  • Installing a Tekonsha Primus IQ Brake Controller on 2019 Subaru Ascent
    The photo you sent looks like it may be what you need to hardwire to the Tekonsha Primus IQ Trailer Brake Controller # TK90160 to as a step of the installation. To install this brake controller in your 2019 Subaru Ascent without the factory tow package you need to start by adding a 4-way, the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118790; I have added a link to an installation video of this connector on a '19 Ascent for you to take a look at. You will also...
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    Image 1 for
  • Trailer Hitch, Brake Controller, and Wiring Recommendation for 2019 Subaru Ascent
    Since you don't have a trailer hitch or wiring on your 2019 Subaru Ascent, I recommend the Draw-Tite Max-Frame Trailer Hitch Receiver - Custom Fit - Class III - 2" # 76253 for the strongest hitch and then the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118790 which has a higher amp rating than the alternative options. It is an easy install and then I recommend using the # ETBC7L and the Curt Echo # C51180 for a brake controller and wiring option that doesn't require...
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  • Can I Really Tow 5,000 lbs With My 2019 Subaru Ascent
    The Draw-Tite hitch part # 76253 for 2019 Subaru Ascent is rated for towing up to 5,000 but only if the Subaru is equipped with an air-cooled continuously variable transmission fluid cooler from the factory and the trailer has brakes. The owner's manual states vehicles without the variable transmission fluid cooler can tow up to 2,000 lbs. It is a good idea to check to make sure your Subaru Ascent is equipped with the cooler from the factory before towing 5,000 lbs. You can find out...
    view full answer...
  • Parts Needed To Tow Trailer With 2021 Subaru Ascent
    The Curt Trailer Hitch Receiver # C13400 you were looking at for your 2021 Subaru Ascent includes everything needed to get it installed. Now since you mentioned you are planning on towing a trailer you will need a vehicle wiring harness # 118790 if your trailer has a 4-way connector, or # 118290 if your trailer has a 7-way connector. In addition if it has a 7-way connector and trailer brakes you will also need a trailer brake controller. I recommend the Curt Echo Wireless # C51180...
    view full answer...
  • Is Curt C51180 Echo Wireless Brake Controller Compatible With 2019 Subaru Ascent
    The Curt # C51180 is compatible with the 2019 Subaru Ascent. If the vehicle has the tow package with the factory 7-way trailer connector, it'll be a plug and play install. If you don't have the factory 7-way, you'll need the # ETBC7L install kit and will need to install a # 118790 4-pole trailer connector. The adapter included with the kit would plug into the 4 pole provided by the # 118790, providing a 7-way. You'd use the wire included in the kit to run a circuit to the positive...
    view full answer...
  • Parts Needed to install a Brake Controller on a 2020 Subaru Ascent
    Definitely glad to hear the EcoHitch # 306-X7381 install went well. This is one of the more difficult installs, so if you were comfortable doing that, installing a brake controller like the Redarc # RED44FR should be pretty straight forward. To start this process, you will need a 4 Flat wiring harness, like the Tekonsha # 118790. This will supply the power needed for the running lights, tail lights, and blinkers. From here, you will need our Universal Installation Kit for Trailer Brake...
    view full answer...
  • Trailer Hitch and Towing Accessories for 2020 Subaru Ascent
    According to Draw-Tite, their # 76253 Class III receiver hitch is a fit for all models of the 2020 Subaru Ascent. The receiver tube exits the rear of the vehicle through the bumper, for better ground clearance at the rear than a standard mount hitch that would have the hitch receiver sitting below the rear bumper fascia. If you'll be using the hitch for towing, you'll need a trailer wiring harness, a ball mount and the correctly sized trailer ball. For a wiring harness, use # 118790....
    view full answer...
  • Recommended Trailer Wiring Harness For 2020 Subaru Ascent
    The Draw-Tite Max-Frame Trailer Hitch Receiver # 76253 you were looking at for your 2020 Subaru Ascent does not include a 4-way wiring harness so you will need to purchase one separately. I recommend Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118790 which is a plug and play harness confirmed to fit your Ascent, and will give you the 4-way trailer connector you are looking for. To complete your towing setup you will also need a ball mount, hitch ball,...
    view full answer...

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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video by:
Joshua S
Employee Dustin K
Video by:
Dustin K
Employee Jacob T
Video Edited:
Jacob T
Employee Chris R
Video Edited:
Chris R
Employee Sarah W
Updated by:
Sarah W
Employee Hannah L
Updated by:
Hannah L
Employee Isabelle B
Updated by:
Isabelle B
Employee Alexander C
Written by:
Alexander C
Employee David F
Test Fit:
David F
Employee Ryan G
Test Fit:
Ryan G

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