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

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

Item # 118648
Our Price: $85.34
You Save: 7%
Custom Fit Vehicle Wiring

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118648 - 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. 1-800-940-8924 to order Tekonsha custom fit vehicle wiring part number 118648 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.
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Tekonsha Custom Fit Vehicle Wiring - 118648

  • 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 behind tail lights
    • Plug in T-connector
  • Includes ModuLite power converter to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects 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: 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 behind the driver's-side and passenger's-side tail lights. You will have to remove the tail light assemblies 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.

T-One Connection Location Points Behind Tail Lights

Once installation is complete, the 4-way flat connector will be stowed in the jack storage compartment of 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.

118648 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Installation Details 118648 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 - 118648

Average Customer Rating:  4.7 out of 5 stars   (240 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.


This worked out great! I absolutely love that they provide a video of how to install it and shows what you need, need to do, and what you'll run into. I had to get creative in making sure the wire that runs from the back to the engine battery was going along a good path that might not get road damage. The rear lights were easy to come off and connect to. The interior panel was easy to take off as well to run the wire underneath. I like that the wire is stored away in the panel door and gets pulled out only when needed to be used because it easily hangs out the back door without any issue.


I have not had a moment to install my hitch and harness, however as with many others apparently, the box arrived opened and the hitch had ZERO packing materials...just a big empty box for the hitch to bounce around. I do see some scrapes and scratches, but nothing that I would return it for. etrailer would be wise to review the comment section and revise how they send their product.

2019 Toyota Sienna

Installation of the hitch, wiring,rear bike rack, and new roof rack towers went well. I didn't set any speed records, but I was more concerned with doing no damage on a new 2019 Toyota Sienna AWD van. The hitch fit up well per instructions except that I was able to work around the exhaust without lowering it. Underbody panel and rear fascia did both need to be removed. Very happy with the end result. The new van is now set up to haul the bikes and canoes and move my log splitter.

2015 Toyota Sienna

I ordered a hitch and the wiring for my new 2015 sienna minivan. The parts came quicker than I could have hoped for. The video instructions made the installation easy, especially since my van was a week old and I really didn't want to mess it up. I have been using the van to tow with for a year now without any troubles. Thanks Etrailer!

2015 Toyota Sienna

Very easy to install. Total wiring time = 45 min. I did not take apart the rear panel by the driver side taillight to run the wire harness. It was a little difficult to fish through due to the size of the connections.


2018 Toyota Sienna XLE. The wiring harness blows my fuse or other wise makes my turn signals not function properly; I've tried connecting them four times and they keep malfunctioning. So I have to keep them disconnected at the tail light assembly. The brake lights work fine.

Etrailer Expert

Mike L.


Is this occurring with a trailer plugged in? There could possibly be a short in your trailer wiring causing fuses to blow. Ill link to a troubleshooting article that will provide some direction for you. If this occurs when the trailer isnt plugged in, you might have a faulty harness that needs replacement. If thats the case, get back with us and well help further.

2017 Toyota Sienna

The kit is perfect, came with everything I needed plus some. The only thing I did different was instead of running a new line back to the battery, I jumped off to the cigarette lighter right next to the rear compartment and put a 1 amp fuse on. My lights are LED so the draw is nothing. Saved a lot of time having to run that wire.


Quality and fitment of products was excellent. Highly recommend install videos on etrailer. The shipping time was very slow. I had some items price matched and that delayed processing a week or more.I provided all links to competitor's products. Very close to month before I received product (it was in stock). That is why I didn't give it an excellent rating.

2019 Toyota Sienna

Install was easy, I watched the instruction video about 3 times and kept it up on my phone to verify my connections when it was time. I had the job complete including all cleanup and mounting the electrical connection to the hitch in about 2/12 hours. I took my time to verify no damage was done to our new sienna.

2020 Toyota Sienna

I guess the packing method is "throw it in a box and hope it gets there. Hopefully etrailer packaging/shipping sees this review and can add the $3 in styrofoam to protect the hitch from going through the box.

2018 Toyota Sienna

Easy installation in the jack storage area. Found a open spot to run power wire throught a harnes grommet so I could run power back to the converter inside and under trim


The installer was very impressed with the product we chose. Thank you!

Toyota Sienna

The T-One Vehicle Wiring harness was easy to install. The video was very helpful, but it could use a description of how to run the power line up to the battery. I ran mine (2020 Toyota Sienna XLE) on the inside of the vehicle until I got to the fire wall then went out through a rubber grommet above the accelerator and brake pedal. I used a trim tool kit to move trim pieces enough to slip the wire under the trim.


The hitch and wiring harness are already installed and work just fine. The shipping timing was fine, BUT the hitch moved around quite a lot in the box as it was not padded, and created a hole in the box big enough that the harness kit could have fallen out of the box.


Excellent hitch, fits flush under the number, about 2 hours to install!


Does not work as stated. Brake tighrs on trailer stays on even when the brake is not press on. ??

Etrailer Expert

Jenny N.


You mentioned that the brake light stays on when the brakes are not being pressed. I would like to help and I have a few questions to ask. Is the brake light brightly lit or is it dimly lit? If you have LED lights, then they may remain on dimly whenever trailer is connected to vehicle. It is recommended to disconnect trailer when parked for extended periods. If it is brightly lit, then it could be that the harness has been overloaded or that there is an insufficient ground or short to ground on trailer or vehicle side. I recommend taking a look at the FAQ that I have listed below. It will provide ways to test the harness and also possible solutions.


Fit perfectly, one man install, paint holding up fine, the reciever is properly sized. Would highly recommend.

2015 Toyota Sienna

Works well. I ran it through the interior of the car instead of under the chassis. Since I don't have a lift; that was a better option.

2016 Toyota Sienna

Superb. I cannot imagine going elsewhere for hitches and accessories. Since I am not too handy I find the videos invaluable as a source of techniques and tips. The kit contained everything necessary for the installation except basic tools. The trailer lights worked first time so what more need be said. I needed the trailer in a hurry but I did not have a way to lift the van so I could only do a temporary job of running the hot lead forward to the battery, with the plan to have my regular auto mechanic redo it correctly asap. You will have to lift the van somehow to do a thorough job of securing that long lead. I wish I had bought dielectric grease, extra double sided tape and extra connectors.

Colin S.


After one year it still works perfectly and I am fully satisfied. Great product and service from eTrailer.

Toyota Sienna

I installed the wiring myself on my Toyota sienna. I did not have a problem with any part of the installation. It took a while but at the same time I was working slowly to make sure I did it right and I was just enjoying working on my van, seeing the under side when running the wiring up to the front. I used an actually fishing pole and stuck it into a hole in the engine compartment to fish it up to my battery. I installed the little dude box right there next to my battery. I had more then enough length of wires which I don't understand why some people complained about it being too long. I actually had about 3 feet left. I ran it under my van and up through the engine compartment to my battery. I was not very confusing to clip to the clip to the appropriate clip on the lights because of the shape. Making sure which side is which was a little confusing but just paying attention to what you are doing will make that an easy job. I'm glad I did it myself.

Kurt Z.


So far I havent had any problems at all. The fuse hasnt blown, the rain hasnt shorted it the circuit. They have worked everytime I hooked up the trailer. Its worked perfectly for me.

Toyota Sienna

This wiring kit made the process of getting trailer lighting installed in my Sienna as easy as it could be, since Toyota does not have a factory harness available. The instructions were clear, though it would have been nice if they were in color. All in all, I was able to follow the instructions and get the kit installed in about the amount of time they specify. Works great!

2017 Toyota Sienna

Easy to install. I did not run a wire up to the battery/fuse block. I installed a cigarette plug on the wire and used the power point near the tailgate. I keep the cigarette plug and trailer plug wires in the jack storage area. I rarely use the trailer lights as my hitch is mostly used for bike racks and a hitch basket.
Shipping was fast.

Etrailer Expert

Mike L.


Drawing the power directly from the battery serves to isolate the tow vehicles sensitive electronics from any short circuits that might occur in the trailer wiring. Connecting the converters power feed anywhere other than the battery or where the converters manufacturer recommends can leave your vehicles electrical system exposed to possible damage, and will also unfortunately void any warranty coverage.

2019 Toyota Sienna

Got the wiring harness in the mail and got it installed the very same day. Easy to follow instructions and was designed for my vehicle. Was able to pick up the travel trailer the next day after installation.

Jim M.


Been on several camping trips with our new trailer receiver hitch and wiring harness is installed on a Toyota Sienna and the 2 respond as 1 vehicle. Very satisfied.

2018 Toyota Sienna

The T-One 4-pole harness was delivered earlier than expected. Installation was very easy, especially after viewing a video that was quite helpful by demonstrating removal of vehicle trim parts. Installation took me about 4 hours total including collecting tools and clean-up. The longest and most difficult task was running the positive wire along the under-body to the battery, since I did not have my vehicle on a lift. The plug now works and we're ready to tow.


Kit fit great , all parts work perfectly muffler shield came loose but got fixed thanks

Show More Reviews

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

  • Total Amp Rating Of Tekonsha T-One Needed For 4-way Connection To Uhaul 5x9 Utility Trailer
    The T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118648 has a maximum amperage of 2.1 amps per circuit for the stop/turn lights and 7.5 amps per circuit for the tail lights. It is designed for a 15 amp fuse, so I can't recommend running the wire to a 10 amp outlet as overloading a circuit could cause a fire. The kit comes with the wire needed for running the 12 gauge wire to the battery and that is my recommendation. It takes a little more work to install but will...
    view full answer...
  • Trailer Wiring Harness Recommendation for 2017 Toyota Sienna
    For trailer wiring harnesses I prefer the Tekonsha brand as they tend to be more reliable over time. So for your 2017 Toyota Sienna you would want the part # 118648 which is a confirmed fit. I attached an install video for you to check out as well.
    view full answer...
  • Trailer Wiring Harness for 2015 Toyota Sienna XLE
    For your 2015 Toyota Sienna XLE you will need the T-One Vehicle Wiring Harness, # 118648. This wiring harness is designed for all models of the 2015 Sienna except the SE. I have included an installation video for you.
    view full answer...
  • Can the T-One Vehicle Wiring Harness for a 2017 Toyota Sienna Be Powered Using the Rear 12 Volt Aux
    The T-One Vehicle Wiring Harness part # 118648 which is a fit for your 2017 Toyota Sienna will need to be powered directly from the vehicle's battery. If you choose to use the rear 12 volt auxiliary power which is not what I recommend then you will need to do so at your own risk. The maximum amp draw for the above trailer wiring harness is separated between two circuits, 7.5 amps for the tail lights and 2.1 amps for the stop/turn signal lights. I have attached an install video that shows...
    view full answer...
  • Install Video to Use for Tekonsha Trailer Wiring Harness on 2017 Toyota Sienna
    I attached the install video we shot for the Tekonsha trailer wiring harness part # 118648 on a 2017 Toyota Sienna. I would recommend following it as a guide completely and you'll have no issues with the harness and would be installing it in a way that wouldn't void the warranty.
    view full answer...
  • Easy Solution for Trailer Wiring Install Harness Installed Backwards 118648
    If I were in your situation I would do exactly what you described. Just swapping the green and yellow wires on the output side of the converter going to the 4-way will take care of the harness being installed backwards without any negative impact at all.
    view full answer...
  • Best Trailer Wiring Harness for a 2018 Toyota Sienna
    The best trailer wiring harness we have for your 2018 Toyota Sienna is going to be the T-One Vehicle Wiring Harness part # 118498 if you have the SE model with features such as daytime running lights, 4.2" color multi-information display, and a premium audio system. If you have the LE or XLE then you will want to use the T-One Vehicle Wiring Harness part # 118648. They both install in the same way which requires you to remove the tail light housings, plugging in the t-one connectors, and...
    view full answer...
  • Recommended Trailer Wiring Harness for 2017 Toyota Sienna XLE
    For your 2017 Toyota Sienna XLE, I recommend the Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118648. This harness plugs into your Toyota Sienna's wiring harness, which is located behind the driver's-side and passenger's-side tail lights. You will then run the included power wire to your vehicle battery. This will power the harness and protect your vehicle's electronics. I've attached a video of this installation and have attached an article to help with...
    view full answer...
  • How Can 2015 Toyota Sienna Transport Two Dirt Bikes
    On a vehicle like your 2015 Toyota Sienna that has a lower tongue weight capacity the only solution would be towing a smaller trailer with a hitch installed like the Draw Tite part # 75237. You'll need trailer wiring too for that which you'd need the Tekonsha part # 118648.
    view full answer...
  • Correct T-One Vehicle Wiring Harness for a 2016 Toyota Sienna L, LE, XLE, or Limited
    If you have a 2016 Toyota Sienna LE then the correct T-One Vehicle Wiring Harness is part # 118648. If you have a 2016 Toyota Sienna SE the the correct T-One Vehicle Wiring Harness is part # 118498. These are both plug-in play options that provide you with a standard four way flat which is the most common. The T-One Vehicle Wiring Harness is part # 118648 also fits any other model expect for SE so if you have an L, LE, XLE, or Limited then this is the correct harness for you.
    view full answer...
  • What Trailer Wiring 4-Way Harnesses Fit a 2016 Toyota Sienna
    If the 2016 Toyota Sienna happen to be an SE model then yes, the trailer wiring from a 2012 like the part # 118498 would also fit it. If it's not an SE model you would need to go with the part # 118648. I attached install videos for both harnesses as well.
    view full answer...
  • Trailer Wiring T-Connector Compatible with 2018 Toyota Sienna SE
    For your 2018 Toyota Sienna SE I recommend the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118498. This is the confirmed fit for the SE model which is slightly different than the other models. It will install in the same way behind the tail light assemblies and with power directly from the vehicle battery to protect your Sienna SE wiring and electronics. I've attached a video to assist as well as an article for help routing that power wire. Once the installation...
    view full answer...
  • Which Trailer Wiring Harness for 2015 Toyota Sienna XLE
    It seems that you have the wrong wiring kit. From the 2015 model year up to the 2021, the Tekonsha # 118498 is only a fit for SE models of the Toyota Sienna which used different taillight assemblies than the other models. For models other than the SE, you'll use # 118648. I've provided a photo showing the differences in the connectors. There isn't an adapter kit, unfortunately. You'll need to install the proper harness kit. I've linked to an install video for the # 118648.
    view full answer...
    Image 1 for
  • Differences in 118648 and 118498 Trailer Taillight Wiring Harnesses for 2017 Toyota Sienna
    The difference between the # 118648 and the # 118498 is the taillight assemblies on the SE model are different, they use different connectors. The 2017 Toyota Sienna SE would use the # 118498 while all other models, including your XLE would use the # 118648. If you click the provided link, you can see an install video for the # 118648.
    view full answer...
  • Trailer Wiring Harness that Fits 2020 Toyota Sienna
    Yes, the Tekonsha 4-way kit part # 118648 that you referenced is the correct trailer wiring kit for your 2020 Toyota Sienna. This installs by plugging inline with the taillights like you can see in the attached install video.
    view full answer...
  • Does a 2017 Toyota Sienna Comes With a Factory Trailer Wiring Harness
    I do not believe a 2017 Toyota Sienna comes with a factory trailer wiring harness but I do have what you need to add one, the T-One Vehicle Wiring Harness part # 118498 for SE trims or part # 118648 for all other trims. These harnesses are both plug and play options that do not require any splicing. I recommend the T-One Vehicle Wiring Harness in particular because they have the best reputation for longevity and reliability. I have attached an install video for you on both options.
    view full answer...
  • Which Trailer Wiring Harness Will Work With 2017 Toyota Sienna LE
    The difference between part # 118648 and part # 118498 is that part # 118498 is designed for the SE model and part # 118648 is designed to work with Siennas that are not the SE model. Since you came from the non-SE model the trailer wiring harness that will work for you is part # 118648. This trailer harness is a simple installation. You just plug it into the connection points behind the driver and passenger side tail lights and then run the hot lead wire to the positive battery post...
    view full answer...
  • Trailer Hitch and Wiring Recommendation for 2015 Toyota Sienna
    For your 2015 Toyota Sienna the Draw Tite hitch part # 75237 would be what you would want. This hitch has plenty of capacity, is priced great and is a confirmed fit for your vehicle. The round crosstube would be it less visible than a square tube hitch as well. I attached an install video for you to check out too. For trailer wiring you would need the part # 118648 which I attached an install video for as well.
    view full answer...
  • Does Hot Lead for Both 4-Way Harness and 7-Way Connector Need to be Run on Vehicle
    The Tekonsha T-One Vehicle Wiring Harness 4-Way Connector # 118648 for your 2017 Toyota Sienna does require that a hot lead be run to the vehicle battery. This hot lead is needed to power the converter for the 4-Way harness and will be separate from the power wire that needs to be installed for a 7-Way kit like # ETBC7. The 12V wire for a 7-Way is ran to the battery for the 12V pin at the connector. Both power wires will need to be run to the battery. I also don't recommend running both...
    view full answer...
    Image 1 for
  • Hidden Trailer Hitch Recommendation for 2020 Toyota Sienna
    For your 2020 Toyota Sienna I highly recommend the Draw-Tite Class III Max Frame Receiver Hitch # 76112. This Class III hitch features the hidden-crosstube design you're wanting (see attached images) and unlike the other hidden options available, it is rated for use with a weight distribution system. The hitch itself features a 3,500 pound towing weight capacity and a 525 pound tongue weight limit. All the necessary hardware is included. If you plan on doing some light towing you will...
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    Image 1 for Image 2 for
  • Trailer Hitch Recommendation for 2019 Toyota Sienna for Towing Pop Up
    You'll need just a few things to tow a trailer with your 2019 Toyota Sienna but let's first start with a hitch. For that I recommend the Draw Tite part # 76112 because it has a 2 inch opening which means it has plenty of towing capacity, has a concealed crosstube which means it's mostly concealed, and because it has a great price. I attached a picture of what the hitch looks like installed as well as a link to an install video for the hitch for you to check out as well. A ball is not included...
    view full answer...
    Image 1 for
  • Trailer Hitch for 2020 Toyota Sienna XLE without Tow Package
    If you are looking to have a hitch installed on your 2020 Toyota Sienna that would indicate that you don't have the factory tow package since that would have been included. For a hitch the mostly hidden Draw Tite # 76112 is a really great option that I would recommend highly. Then for trailer wiring the Tekonsha kit part # 118648 is an easy to install and very reliable option as well.
    view full answer...
  • Trailer Hitch Recommendation for 2017 Toyota Sienna
    Since all of the trailer hitches for your 2017 Toyota Sienna require some underbody trimming, and for a few more reasons that I'll get into, the best option is the Draw Tite trailer hitch part # 76112. This is a 2 inch hitch which is the most popular size and has the most capacity, it has a concealed crosstube so it will be less visible than most, and would not require a stabilizer strap like the Curt hitch would if you ever carried a bike rack. I attached an install video for more info...
    view full answer...
  • Does Power Wire of 2018 Toyota Sienna Have to Run to Battery
    Not all vehicles can handle the additional amperage draw of the trailer taillights on the vehicle taillight circuits. Those vehicles need setup that draws power from the battery. Some vehicles have higher rated circuits that can handle this, and others need to have the power drawn straight from the battery to protect the taillight circuits. If you run the wire to a power outlet on the vehicle you could potentially short it out as well in the event of a short. It also would void the warranty...
    view full answer...

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Info for this part was:

Employee Mike L
Expert Research:
Mike L
Employee Michael H
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Michael H
Employee Jameson C
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Employee Jeffrey L
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Employee Joshua S
Video Edited:
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Employee Jacob T
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Employee Kathleen M
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Employee Dustin K
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Employee Laura H
Written by:
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Employee Cole B
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Test Fit:
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Employee Brent H
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Brent H
Employee Robert C
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Robert C
Employee David F
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