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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 # 118749
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Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector 4 Flat 118749
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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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system. Call 800-298-8924 to order Tekonsha custom fit vehicle wiring part number 118749 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 (2)
  • Q & A (3)
  • Videos (3)
  • Photos
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Tekonsha Custom Fit Vehicle Wiring - 118749

  • Custom Fit
  • Trailer Hitch Wiring
  • Tekonsha
  • 4 Flat
  • 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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system.


  • Provides a 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights
    • Compatible with 5-pole, 6-pole and 7-pole adapters (sold separately)
  • Connects quickly and easily
    • Locate connection points in rear cargo area
    • Plug in T-connector
    • Run hot lead to car battery
  • 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: 4.2 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 inside your rear cargo area. You will have to remove the cargo door and some interior paneling 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.

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.

118749 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

Installation Details 118749 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

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

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Tekonsha T-One Vehicle Wiring Harness Installation - 2017 Kia Niro

Shane: Hi, I'm Shane with etrailer.com. Today on your 2017 Kia Niro I'm going to walk through how to install Tekonsha T-One vehicle wiring harness with four-pole flat trailer connector. Adding wiring to your vehicle is going to allow, if you're pulling a trailer, to get wire functions from your vehicle to your trailer so that you're legal and safe.Adding this wiring harness to your vehicle, for the Tekonsha wiring, in my opinion, is probably going to be the best choice. Tekonsha's been known to hold up in their wiring. They're going to have a converter box that's going to be filled with potting material where all the wires come in and connect. That potting material holds those wires onto that circuit board really well so that, in the event that there is a lot of movement in that box or with the box, vibration, those wires aren't going to come loose.Another thing I like about it is, with the converter box, what it does is it actually protects your factory wiring in your vehicle from any backfeed from the trailer if there's a wiring issue.

What happens is, if there's a wiring issue that backfeed comes back in and that box is going to stop it from getting to your factory wiring on the vehicle. As I mentioned, this is going to be a four-pole connector. It's going to give you your proper lighting functions, your brakes, turn signals, and your running lights. It's going to come with a nice dust cap so when not using it, it's going to help protect your connections from any dirt and debris. This wiring harness is going to live inside the vehicle, so when you're not using it you simply raise up your panel.

You can roll it up and store it in the compartment. When you're ready to use it, you pull it out. Make sure you stay away from anywhere where it connects or where your hatch attaches. You're going to run it right over this rubber seam, close your hatch, and connect to your trailer.This wiring harness is going to have 4.2 amps per circuit for your stop and turn signals and 7.5 amps for your taillights, which means, having the 7.5 for your taillights, if you have a few extra lights on your trailer, those lights are not going to be dimmed. Another nice thing about it is, this is powered by the battery.

It's going to connect, be tying each taillight to the factory plugs, but you have a power wire that goes up and connects to the battery. So, the only thing that this is drawing power from is the battery. It's only getting its signal from the lights. So, as I mentioned, the extra lights on the trailer. If it was drawing power from the lights, not only would the trailer lights dim, but the lights on the car would also dim.

Since we're getting power from the battery, those extra lights, they're going to stay nice and bright so that everybody can see you.Now that we've gone over some of the features, let's walk through how to get it installed. To start our installation, we need to remove our floor coverings from the back of our vehicle. Take a Phillips head screwdriver. We're going to take out this screw, this one, and this one on both sides of the vehicle. Once you get them removed, you're going to pull out the panel and set it aside. Then we need to remove our threshold. We're just going to pull up on it and set it aside. We're going to have a screw in the bottom corner of each panel. Remove that one. Then if we come down here inside, we're going to have one right down here. We'll do that on both sides.Then for our compartment in the back, we're going to have two screws on each side we need to remove. We'll set that one aside. We're going to take a trim panel tool and we're going to come up to this panel here. Then we're going to pop it out like that to get access to that bolt. We're going to do this on both sides. Take a 10mm socket and remove the bolt. We need to pull our panel out so we can access our wiring. Wiring going to our taillight is going to be this one here. On one side you're going to see a little square tab. You're going to push that tab and then separate your wires. We're going to do that same thing on the passenger side.Next we're going to take our wiring harness that comes in our kit. Our black wire that's coming off of our converter box, we're going to go ahead and add on a yellow butt connector. You're going to get a bundle of wire like this. This is going to be routed up to the battery in the engine compartment. What we're going to do, before we get it mounted back behind that panel, we're going to go ahead and attach this wire to the wire on our converter box. So we'll strip back one end, go ahead and add it on just like that. Now we're going to take the yellow core, or yellow end. We're going to pull back our panel and we're going to connect it to the two wires that we just separated. One. Push it until you hear it click. The other side goes into the other one. Right back in there. Our green wire and your red wire are going to route straight over to our passenger side, and we're going to connect it behind the panel the same way we did on our driver side.Next we need to mount our converter box. We need a flat spot. Kit's going to come with some two-sided tape. Go ahead and stick it on there. Make sure you push down on it to get a good hold. We're going to ground our white wire about the here. You just want to make sure it's on a metal surface. Kit's going to come with a self-tapping screw. Then we can route our green wire over and connect it to our passenger side. The black wire, right down here there's a rubber grommet. We're going to poke a little hole in it and we're going to feed our power wire right through that grommet. It's going to come out in the bottom of the vehicle.Once you're done with everything inside you can go ahead and reinstall all of your panels. Your wiring that you felt through the rubber grommet is going to come out right back behind the fascia here. What I did, to run it to the front of the vehicle and make sure it was staying away from anything hot or moving. Where our exhaust is here, our wire's going to come out, like I said, right in here somewhere. What I did is I went over top of my hitch, my heat shield right up here. I actually have it up above that above my axle. Came over top here. Take a 10mm socket and you're going to have a nut here and a nut down on that end. Pull this panel down, and then we can take our wire and we're going to tuck it right up underneath this panel all the way up to the front of the vehicle. It'll come out right there. Once we get up here, we need to get it up into the engine compartment. You can use air line tube, you have a piece of wire or something. Again, make sure you're staying away from anything hot or moving. For instance, your CV axles. You want to make sure you're staying away from them, anything that has to do with your steering and moving.What I'm going to do is I'm going to run it right up along my frame rail right here. See where I pulled my wire up right here. Zip tied it right there to that metal bracket. Cut back my wire to size because I'm going to attach it right underneath this panel. Your kit is going to come with another butt connector. I would suggest it trading it out for a heat shrink to help protect those connections from corrosion. You're going to take your fuse holder, cut it in half. Then we're going to strip back both ends. One end you're going to put on a ring terminal. The other end is going to go on the butt connector. Then we'll take our source and shrink that up.We're going to pull off our fuse panel cover. We're going to add two connections here. We're going to use the one here on the left. Really you could use either one. You want to make sure, when you make this connection, your fuse is not in the holder. Put on your ring terminal, then reinstall it. Once you have that done, I'm going to zip tie my wire right about here just to hold it up. We can go ahead and reinstall our fuse just like that. Now we'll test everything out using part number I26. Left turn, right turn, brake lights, running lights. Once you've tested everything out, you're ready to go. That's going to do it for a look at and installation on the Tekonsha T-One vehicle wiring harness with four-pole flat trailer connector on your 2017 Kia Niro.

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118749

Average Customer Rating:  5.0 out of 5 stars   (2 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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system.

- 118749
2017 Kia Niro

great quality and very good detailed video for installation 775127

- 118749
2017 Kia Niro

Exactly as described, works like a char m! 510990


Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Can Trailer Wiring for 2019 Kia Niro be Used as Tow Bar Wiring in Reverse
    We have tow bar wiring solutions that will work great on your 2019 Kia Niro but trailer wiring does not work in reverse so you wouldn't be able to use the kit you mentioned. For lighting you can use the diode kit, # RM-15267, and not have to worry about cutting into the taillight housing. This will splice into your taillight wiring to allow your tow vehicle to control the taillight assemblies of the towed vehicle. This comes with a round 6-way connector that you will install on the...
    view full answer...
  • Wiring Harness Fits for 2018 Kia Niro
    The wiring harness fits we have for the 2018 Kia Niro, which include Curt part # C56376 and Tekonsha part # 118749 that you purchased, specifically exclude fitment on the plug-in hybrid version of the car. You'll see this notice on the linked page. If you have the plug-in hybrid we do not have a trailer wiring harness for it. I did check with my technical contact at Curt about installing wiring in your vehicle. He said that a Niro plug-in hybrid owner has reported using a 12V circuit...
    view full answer...
  • 2019 Kia Niro Ex Hitch Recommendation
    I checked with Curt and the Curt Trailer Hitch Receiver # C13329 is a confirmed fit for the non-PHEV version of the 2019 Kia Niro like what you have so this would work well for you. It's a Class III hitch with a 2 inch opening and has a concealed crosstube so it's less visible than other hitches. If you need trailer wiring too we have the T-One kit part # 118749 would be what I recommend. It's a custom fit that won't require any splicing and it has the most reliable converter box of...
    view full answer...

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Info for this part was:

Edited by:
Lindsey S
Expert Research:
Jameson C
Video by:
Joshua S
Video by:
Jacob H
Video Edited:
Jacob T
Video Edited:
Dustin K
Installed by:
Cole B
Written by:
Alexander C
Test Fit:
Shane H
Test Fit:
Ryan G
Updated by:
Isabelle B

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