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T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector

T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector

Item # 118278
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Custom Fit Vehicle Wiring

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118278 - Powered Converter 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 OEM tow package harness - no cutting, splicing or tapping required. 1-800-496-5010 to order Tekonsha custom fit vehicle wiring part number 118278 or order online at Free expert support on all Tekonsha products. Guaranteed Lowest Price and Fastest Shipping for T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
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  • Reviews (111)
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Tekonsha Custom Fit Vehicle Wiring - 118278

  • 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 OEM tow package harness - no cutting, splicing or tapping required.


  • Provides a 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights
    • Designed for use with a factory tow package
    • Compatible with 5-pole, 6-pole, and 7-pole adapters (sold separately)
  • Connects quickly and easily - no cutting or splicing of wires
    • Locate connection points 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
  • 1-Year limited warranty


This custom-fit T-One connector plugs into your vehicle's factory tow package wiring harness, which is located in your rear cargo area. You will have to remove the rear threshold plate and interior paneling to access this harness.

Once installation is complete, the 4-way connector will be stowed beneath your vehicle, near the trailer hitch. A mounting bracket (sold separately) is recommended to keep the connector secure.

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.

118278 Tekonsha T-1 T-Connector - OE Replacement - 4-Way

Installation Details 118278 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Reviews

T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector - 118278

Average Customer Rating:  4.9 out of 5 stars   (111 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 OEM tow package harness - no cutting, splicing or tapping required.


So far so good. Have yet to trailer anything. Wiring harness is pretty straight forward but takes a little patience taking off panels.


I have purchased items in the past and had great customer service. This last purchase there was an issue with my order and it didn’t arrive for almost 4 weeks. At that point I did not need the part any longer. I should not have had to pay for return shipping because the issue was with etrailers not getting the item to me in a reasonable amount of time.

2016 Mazda CX-9

If you have a 2016 MAZDA CX-9 - this kit WORKS. It appears all 2016 Mazda CX-9's have the trailer wiring harness already installed. It is located behind the rear passenger side interior panel - the Tekonsha instructions show you how to get to it.

You do NOT need to get a "generic" wiring kit as many of the other responses are suggesting. Just plug this one in and it works.

I have submitted pictures below of the installation on my vehicle. I also installed the 76020 Draw-Tite Class 3 Trailer Hitch Receiver which fit nicely.


I guess I thought the hitch had a mounting bracket to mount the 4pin bracket to. No biggie, I just drilled a couple holes and mounted. Maybe I didn’t do right? Regardless, this will work. Thank you

2022 Mazda CX-9

2022 Mazda CX-9, installed just like the video. Great instructions, awesome turnaround time, and a wealth of information on the site.


As always, great service and information at etrailer.


Installed on a 2020 Mazda CX-9. So far so good. Works great, with no issues!

2022 Mazda CX-9

Received UPS delivery today, package was torn in a couple of places, exposing small portion of hitch damaging paint along back side of receiver (not a big deal). Driver did ask if I wanted to return shipment. I'll prime and paint 1-2 inches of scratched metal edge. Other than that, great service and product as always.. Really appreciate the videos for installation instructions.


Worked out well, wasn't the most intuitive thing to install but still a good experience.


The product was shipped quickly and its about 5-6 months now using it and it works as advertised.

2016 Mazda CX-9

Nice product and easy to install the "Draw-tite Max-frame Trailer Hitch Receiver" with T-One wiring harness for Factory Tow Package- 4 Pole Flat Trailer Connector...

2022 Mazda CX-9

Product arrive quickly and was exactly as advertised. The installation videos were fantastic and really sped up my installation process.


The hitch looks so nice and durable
shipped so fast And the price are fair
I will recommend to anyone who is looking for a great hitch

2022 Mazda CX-9

Worked perfect. Great video to help make installation easy to understand.


Great service and Delivery, Justin B. Was very helpful with products, His knowledge and expertise answered All questions. product arrived a day early which was very pleasing and much needed !! Product installation videos made it a snap to install, and wire installation tools that came with hitch hardware made installing bolts in frame so easy. Using a strap to support exhaust was a great recommendation !! Every part fit perfectly and operated as specified. Wiring, Hitch and bracket took me approximately 2.5 Hrs. doing this on my driveway. These components were installed on my 2017 Mazda CX-9 AWD. I did not take any photos because what you see on E-trailers videos is exactly how it looks.


Took about 45 minutes to install. Just follow the installation video and you can't go wrong installing this.

2020 Mazda CX-9

Worked flawlessly, videos were very hel pful.

2018 Mazda CX-9

I wish Etrailer would consult every company I shop with on how to create an amazing buying experience. From finding what you need, to installation videos - Perfection!


Followed videos which were for my exact vehicle. The videos are really helpful. Anybody can put the hitch on and install the wiring harness. I probsbly saved $600 doing it myself.

2016 Mazda CX-9

This is in reference to a 2016, Mazda CX9. This comment adds to the 2 previously posted comments. It deals with getting the interior panel to release. There are 2 screws that must be removed before attempting to remove the panel. One screw is at the top of the panel under the black plastic hook.The other screw is under a piece of plastic trim that must be removed where the lower chrome anchor is. Then remove the jack, and the other plastic parts near the jack. Once everything is removed, carefully start popping the trim panel off with a trim panel pry tool. Keep prying until you can reach the plug that part #118278 goes into.

It is only a 4-wire harness. I really need a five wire for my boat trailer. I wish ETRAILER had a five-wire.
Marty W - 10/07/2017

2019 Mazda CX-9

I installed in about 45 min. Very easy to do if you follow along with the video. This is my second etrailer elect kit. Great product!!!

2019 Mazda CX-9

Perfect match with the vehicle. Plugged right in and works!

The installation video provides step-by-step instructions for pulling panels and removing anchors. The electrical installation took less an hour and looks clean.


Harness was simple to install, and has worked great for last year.


One year in and this wiring harness is working like a charm. I would recommend it to anyone looking to hook up electrical to a tow vehicle. Instructions were simple with minimal tools required. If I need anything tow related is my first go to.

2019 Mazda CX-9

This kit installed seamlessly on our 2019 Mazda CX-9. The instructional video from etrailer perfectly walked me through step-by-step which was very reassuring, since I'd probably have been a LOT more delicate removing the necessary side panels in the back of the SUV without it. Just like the trailer hitch I purchased, the instructions were spot-on and made installation of this wiring harness an absolute breeze. etrailer has definitely set the bar on installation and support for their products.

Show More Reviews

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

  • Trailer Wiring Recommendation that Fits 2018 Mazda CX-9
    Actually the trailer wiring harness part # 118278 is a confirmed fit for the 2018 Mazda CX-9. I attached an install video for you to check out as well.
    view full answer...
  • Does Tekonsha Trailer Wiring Harness Fit 2018 Mazda CX-9 Grand Touring
    The Tekonsha trailer wiring harness part # 118278 is a confirmed fit for all models of the 2018 Mazda CX-9 so it does fit your Grand Touring model.
    view full answer...
  • Best Trailer Wiring Harness for a 2014 Mazda CX-9 with Factory Tow Package
    I do have an option for you but the T-One Vehicle Wiring Harness for Factory Tow Package part # 118278 is not a confirmed fit for your 2014 Mazda CX-9. Instead, you will want to use the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part # 118520 which fits models both with and without the factory tow package. The wiring harness that you originally asked about is only a confirmed fit for a Mazda CX-9 from 2016-2018 and will not work on your 2014. I have also attached an...
    view full answer...
  • Installing 5-Way Connector on 2016 Mazda CX-9
    There is not a 5-Way connector available that is designed to install on your 2016 Mazda CX-9. With this in mind, the best solution is still to install a 4-Way connector with the Tekonsha # 118278 and use the Wiring Adapter # 20036, which is what it sounds like you are doing. The harness and adapter will give you the 5-Way needed to connect to your trailer.
    view full answer...
  • Installing a Draw-Tite Hitch on a 2021 Mazda CX-9
    The Draw-Tite # 76020 does have a tech tip of needing to modify the heat shield as it does fit a few years of the Mazda CX-9. Some of the 2018 models did need this shield modified slightly to fit properly, but it looks like that may have been limited to that year. I have an install video we did on a 2020 CX-9 and there was no modification needed. As we have not had a 2021 to do an install on as of yet, I can't 100% confirm the need to modify the heat shield, but odds are you will not need...
    view full answer...
  • Does Draw Tite Hitch # 76020 Fit 2022 Mazda CX-9
    Yes, the Draw Tite hitch part # 76020 does fit your 2022 Mazda CX-9. If you needed trailer wiring too the Tekonsha part # 118278 is a confirmed fit, installs easiest, and has the most reliable converter box.
    view full answer...
  • Trailer Wiring Harness Recommended for 2012 Mazda CX-9
    Some vehicles are partially prewired at the factory for the trailer connector, but the 2012 Mazda CX-9 didn't have that provision. I'd recommend going with the Tekonsha T-One connector, part # 118520 as their hitch wiring harnesses seem to be a bit more reliable in the long term. If you haven't chosen a hitch yet, I'd recommend the Curt Class III, part # 13575. I've linked to installation videos that you might find helpful.
    view full answer...
  • Is There a Class II Hitch with 2 Receiver Available for the 2020 Mazda CX-9
    I have a solution for you, but there is not a Class II hitch with a 2" receiver available for the 2020 Mazda CX-9. Instead, you can use a Class III hitch like the Draw-Tite # 76020 which has a 2" hitch receiver like you're seeking and also has a hidden cross-tube like the EcoHitch so it's going to keep the clean factory look on your CX-9. If you're going to be towing with your CX-9, you'll also need a wiring harness, ball mount and hitch ball. For the wiring harness I recommend using the...
    view full answer...
  • Recommendation for Adding 5-Way Trailer Connector to 2019 Mazda CX-9
    On your 2019 Mazda CX-9 there is a factory port behind the passenger side trim panel that accepts a custom 4-Way trailer harness plug. If this is what you are referring to when you mentioned that your vehicle has the trailer ready connector, then you will want to start with the Tekonsha T-One Wiring Harness # 118278. This will plug right into that factory port to provide you with a 4-Way connector. From there (or if you already have the 4-Way connector) I recommend simply adding the Tow...
    view full answer...
  • Trailer Hitch and Wiring for 2020 Mazda CX-9
    We have a Draw Tite Class III part # 76020 as a confirmed fit for your 2021 Mazda CX-9 that I would recommend highly as it's mostly hidden and has great towing capacities. Then for a custom trailer wiring harness we have the Tekonsha part # 118278 which installs easily and has a very reliable converter box. If you wanted to do some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4...
    view full answer...
  • Hidden Trailer Hitch Recommendation for 2019 Mazda CX-9
    The most hidden and best hitch option for your 2019 Mazda CX-9 is the Draw Tite hitch part # 76020 as only the hitch opening hangs below the rear bumper and it has a 7-way bracket built into it which will make mounting a 7-way like you are wanting as easy as possible. I attached an install video and picture for this for you to check out as well. For trailer wiring you'd need to start with a 4-way like the part # 118278 which installs easily and then you'll need to convert it to a 7-way...
    view full answer...
    Image 1 for
  • Parts Needed to Tow Small Utility Trailer with 2017 Mazda CX-9 Equipped with 1-1/4" Hitch
    In order to pull a 4x6 utility trailer with your 2017 Mazda CX-9 you will need to add a wiring harness and ball mount/hitch ball combo. Starting with the wiring harness I highly recommend the Tekonsha T-One # 118278. This custom harness simply plugs into a factory port behind the passenger side trim panel for a complete "plug-and-play" install. This will provide you with a 4-Way connector to connect with and power the trailer's basic signal lights. I have attached an install video on...
    view full answer...
    Image 1 for
  • Trailer Hitch and Wiring for a 2021 Mazda CX-9
    The Draw-Tite Max-Frame Trailer Hitch # 76020 is going to be a great option for your 2021 Mazda CX-9. This hitch has a concealed cross tube and good towing capacities. It has a 2" receiver opening and includes an integrated mounting point that lets you attach a bracket for a 4-way like the T-One Vehicle Wiring Harness # 118278, which is the correct wiring harness for your CX-9. The T-One connector plugs into your vehicle's factory tow package wiring harness, which is located in your rear...
    view full answer...
  • Parts Needed to Add 5-Way to 2020 Mazda CX-9
    To install a 5-way on your 2020 Mazda CX-9 will require you to first install a custom fit 4-way like the # 118278 and then use a 5-way adapter like part # C57187 which plugs into the 4-way and requires you to run the extra wire to the reverse light circuit of the vehicle. Since 5-ways aren't nearly as popular as 4-ways they aren't available as plug and play options.
    view full answer...
  • Recommended Trailer Hitch Receiver for 2019 Mazda CX-9
    For a hitch that is confirmed to fit your 2019 Mazda CX-9 I recommend the Draw-Tite Max-Frame Trailer Hitch Receiver # 76020. This is a custom-fit Class III hitch with a 2" receiver. It has a concealed cross tube so only the receiver will be visible at the back of your vehicle. This hitch has a max gross trailer weight of 4,500 lbs, max tongue weight of 675 lbs, and is compatible with weight distribution. It features a bolt-on installation and a limited lifetime warrany. If you plan on...
    view full answer...
  • Recommendation to Install 5 Pole Connector on 2017 Mazda CX-9
    If your 2017 Mazda CX-9 already has a 4-Way connector installed, I recommend using the Tow Ready 4 Pole to 5 Pole Trailer Wiring Adapter # 20036. This will easily change the 4 pole flat on the vehicle to a 5 pole flat. The additional blue wire will simply get spliced into the reverse light wire on the CX-9 with the included quick splice connector. You can use a circuit tester like # 3808 to determine which wire is the reverse wire on your vehicle. If you do not have a 4-Way already installed...
    view full answer...
  • Determining Towing Capacity of 2017 Mazda CX-9 with Draw-Tite Class III Trailer Hitch
    The Draw-Tite Class III Max Frame Receiver Hitch # 76020 referenced in your question is confirmed to fit your 2017 Mazda CX-9. As you mentioned, the 2 inch hitch features a 4,500 pound towing weight capacity and a 675 pound tongue weight capacity. I took a look at the online owner's manual for your CX-9 and found a towing capacity of 3,500 pounds. A towing setup is always going to be limited by its weakest component. This simply means that the weight of your trailer will need to fall...
    view full answer...
  • Can the Tekonsha Wiring Harness # 118278 Fit a 2016 Mazda CX-9
    The Tekonsha Wiring Harness # 118278 is only confirmed to fit 2016 Mazda CX-9's with a factory tow package. If you do not know if you have a factory tow package, you can check behind your rear trim panels to see if you find the factory connectors. If you find factory connectors, you can use a circuit tester like part # 40376 to probe the connectors to see if they are active with taillight functions. If not, you will have to check with your dealer to see if the factory connectors can be...
    view full answer...
  • 4-Way to 5-Way Adapter Recommendation for 2016 Mazda CX-9
    The back up circuit will be found at the reverse light harness of the vehicle. You will need to find the circuit that carries 12 volts only when the vehicle is in reverse that runs to the reverse light circuits of your 2016 Mazda CX-9. For an adapter to convert the 4-way to a 5-way you will want the part # 20036. To find the circuit you will need a tester like the part # PTW2993.
    view full answer...
  • Which Curt Hitch Fits 2020 Mazda CX-9
    Yes, the Curt hitch part # C13284 that you referenced is confirmed as a fit for your 2020 Mazda CX-9. For trailer wiring the Tekonsha part # 118278 is a confirmed fit and easy to install as well! I attached install videos for both of these for you to check out too. If you wanted to do some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4 inch rise or 4 inch drop. It also includes...
    view full answer...
  • Recommended Trailer Hitch for a 2020 Mazda CX-9
    The trailer hitch I recommend for a 2020 Mazda CX-9 is the Draw-Tite Max-Frame Trailer Hitch Receiver part # 76020 because it has a hidden design which means only the receiver tube is shown therefore you get a very sleek look, there is an integrated trailer connector tab which cuts down on your total list of parts, and it has the highest weight capacities available so you know it will be strong and last a lifetime. I have attached an install photo for you. If you will be towing then you...
    view full answer...
    Image 1 for
  • Will T-One Connector Fit 2018 Mazda CX-9 With or Without OEM Hitch
    According to my research, and my contact at Tekonsha, the 2016 and 2017 CX-9 models both came with the connector for the T-One # 118278 as a standard. Since your 2018 Mazda CX-9 is the same generation it would be surprising if you didn't have that connector. I did check the online version of your owner's manual and it states on page 6-58 that the #8 "Trailer Hitch" fuse is only included on some models. You may want to check the left side of your fuse block compartment to make sure that...
    view full answer...
    Image 1 for Image 2 for
  • Recommended Hitch and 4-way Connector for a 2021 Mazda CX-9
    The hitch that I recommend for your 2021 Mazda CX-9 is the Draw-Tite Max-Frame Trailer Hitch Receiver # 76020.This hitch has a bolt-on, no-drill installation and will provide you with a 2" receiver opening which is the most common size used for hitch mounted accessories such as bike racks, cargo carriers and ball mounts. This hitch also includes a bracket you can use to mount the Mounting Bracket 4-Pole Flat # 18144 on for mounting your 4-way connector to your hitch. The 4-way wiring harness...
    view full answer...
  • Trailer Wiring and Hitch that Fits 2022 Mazda CX-9
    We have trailer wiring that fits your 2022 Mazda CX-9 with the Tekonsha kit part # 118278 but the Curt you mentioned is not a fit for your vehicle. This will work great with the Draw Tite hitch you plan on installing on your vehicle as well # 76020.
    view full answer...

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