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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 # 118745
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118745 - Custom Fit 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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system. 1-800-496-5010 to order Tekonsha custom fit vehicle wiring part number 118745 or order online at 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 (21)
  • Q & A (0)
  • Videos (4)
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Tekonsha Custom Fit Vehicle Wiring - 118745

  • 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 - 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 storage trays 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.

118745 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

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 - 2018 Buick Encore

Today on our 2018 Buick Encore, we're going to be taking a look at and installing the T1 vehicle wiring harness with 4-pole flat trailer connector. This is what our wiring kit looks like installed. As you can see we have more than enough length here to stretch out to our trailer. This is going to give you all your necessary functions including brakes, running lights, left blinker and right blinker. You don't have to cut or splice into your factory harness. It's simply plug and play.

What I really like about this wiring kit is the module box. What that does, it protects your vehicle in the case of a short. So if your trailer shorts out, you do not have to worry about it affecting your vehicle's wiring. Another nice thing I like about this wiring is that when you're not using it, you can simply roll it up, lift open your cover, and store it down here out of the way.Then when you want to use it, go ahead and get it out of your cover, and just go ahead and line it up with your weather stripping here. You want to stay away from any latches.

That way when you close it, it doesn't get pinched. Now we're good to go.To begin our install, we're going to go ahead and open up our hatch, remove our cargo cover. Go ahead and set this to the side. Next we'll remove these two spare tire compartments, and on each side there is going to be a T40 torch fit screw. After we get these removed, you can just go ahead and set them off to the side for now.

Now we're going to remove this threshold here. There's going to be two, 10 mm bolts holding it in place. Now with a flat blade screwdriver, we're going to remove this trim panel here. There's a little recess in the plastic. So that'll allow us to get our blade in there.

Just pry out. Break it free, then you can just use your hand and wiggle it around. Sometimes these are tricky if they've never been removed, so just be careful not to break any of the tabs, and take your time. Just set it to the side for now.On the passenger side we have a similar situation here. Just remove this panel with your hand. Now you can see this panel. That's what we're going to be removing. Put our flat blade screwdriver in, just pry up on it. Over here on the driver's side, you're going to be disconnecting this connector here. All you do, and there's a tab right here, you push that in with your hand and pull outward, and they'll separate. Now we need to run the yellow and brown wires off of our new harness up through here, through our connection point. You can do this with your hand, or a coat hanger, something you might have handy laying around that you can use. Now we'll take our factory connector that we unplugged from the taillight, and with our new connector on our harness, we're going to plug it in until you hear it click. Now the other end, this will plug into our factory taillight connector that we removed this one from. Now what we're going to do is take our red and our green wires from our new harness and run them through our threshold here to the other side.I've gone ahead and ran a pull wire through, just to make it a little bit easier to get our wires through. Go ahead and pull them through. All right, now on the passenger side we want to disconnect this harness, just like we did on the driver's side. Now we'll go ahead and run our green and red wires up through this compartment here, just like we did on the driver's side. And just like we did on the other side, we'll go ahead and connect to our factory harness. We'll take this connector and go right to the taillight. Now we're going to go ahead and run our power wire. We're going to run it through this grommet here. So we're going to have to remove that, that's what it looks like. What I went ahead and did, was take our pull wire and ran it through the hole where our grommet was. We came out underneath, so what I did was, I took the long black power wire that comes with our kit, and taped it to the end of the pull wire.That way we'll pull the wire back up, and our power wire will go inside of the car. Now we'll take our grommet that we removed earlier. We'll take a razor or drill or something, be careful while you're doing this, and just poke a hole in it. Then we can take our power wire and feed that through, and we'll reinstall the grommet. We went ahead and got some black silicone and smeared it around the hole in the grommet just to keep it nice and sealed. We need to go ahead and strip our power wires, and using a butt connector that comes with our kit, go ahead and crimp that down on one end. Connect the other end to the black wire that comes out of the module like so. I went ahead and put some electrical tape around our butt connector there, just to ensure a nice seal. Now we're going to install our converter box. We chose a nice, flat area here, that's out of the way. We cleaned it off with some rubbing alcohol.Now we're going to use our double-sided sticky tape from the kit. Go ahead and pop that on our box. Make sure it's on there nice and good. Remove the other side, you want to stick it on there. Now we're going to ground out our white wire here. We want to choose a spot that's flat and out of the way, and also metal to metal contact. So right here's a good spot. Going to use our soft tapper that comes included with the kit, and a 1/4" drive to screw it in. Now that we're all done back here, we went ahead and just tidied the wires up a little bit with a few zip ties. So now we can go ahead and run our main power wire up to the front. I can show you how to do that here in a moment. All right, here's how we ran our power wire. We came out through our grommet, ran it up here and zip tied it along the brake line.Now you do want to avoid anything that's going to be hot, or any moving parts, so keep that in mind. Run it up along through here next to our evap canister system. Underneath this bracket, then we actually ran it through our frame rail. You can use a pull wire to help you with that. We dropped it out right here. On the other end, we put our pull wire and we're going to pull it up through the engine bay to hook up to our battery. I'll go ahead and pull our pull wire up through the engine bay, and on the other end here, we have our power wire that we ran. So we pull it up to get all the slack out of it, there we go. Next we're going to prepare our fuse holder here. Just cut it in half in the middle. Take your wire strippers. Now on one end we will use a heat shrink butt connector, since there's somewhat outside under the hood. You can find these on'll crimp it on. Trying to get a little more wire exposed here. On the other end we'll use our ring terminal that is provided with the kit. Go ahead and get that crimped on. With our fuse holder prepared, we can go ahead and trim any excess power wire we might have. Go ahead and strip that in and connect our fuse holder. Now we'll go ahead and shrink our heat shrink ends here with our heat gun. Be mindful where you point this, because it is really hot. You don't want to melt anything under the hood or catch anything on fire. We're going to connect our ring terminal end to this positive stud here. The nut will be a 12 mm. Go ahead and loosen that up. Put it on, and don't forget to snug it back down. We went ahead and put a little notch in our plastic cover here, just to help accommodate this wire so it's not jammed so much. Once we're all hooked up, we can go ahead and insert our fuse, and close your dust cap.Now that all our wiring is complete, you want to make sure and test it before we finish putting all the panels back together. So here we're going to be using a tester that you can pick up on So I make sure our running lights work. All right. Our brake lights, okay. Our left turn, all right, and our right turn, okay. Everything seems to be working. Now that we've verified all the wiring is worked, we can go ahead and put all our panels back together. That will complete our T1 vehicle wiring harness with 4-pole flat trailer connector install on our 2018 Buick Encore.

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118745

Average Customer Rating:  4.9 out of 5 stars   (21 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.

2019 Buick Encore

The package shipped an hour after I ordered it and showed up a day quicker than advertised. It looks right and if it hooks up and functions as it is supposed to I will be SUPER happy. From reviews I’ve read it sounds like tech support is great but I have a buddy who teaches people to drive tractor trailers and he’s very good with stuff like this, so I’ll probably just let him hook it all up. I’ll add pictures later, I won’t be needing to use the trailer until our house is done being built. More to follow.

2020 Buick Encore

I was suprising pleased how easy it was to install this wiring kit. It's mostly all plug and play connections except for a grounding wire and getting a hot wire from inside rear of vehicle to the battery in front. All the videos show that you just remove a black rubber cap slice a hole in it feed the wire through it and snap the cap back in place. But on my 2020 model the rubber cap was already being used by a factory wiring harness so you had to make a hole in the cap beside the wiring harness that was using this space. Other than that and fishing the hot wire around brake lines up through the frame up to the battery ( not hard just time consuming) it was a fairly easy installation. I definitely give this kit a thumbs up!!!


The hitch was sent on time and in good condition, the installation was easy and fast, instructions were easy to follow, electrics kit was plug and play. Only downside is after 1 year the paint on the unit is starting to peel and rust is forming


Ashley was the epitome of professional while being very customer-centric while taking care of me.

2017 Buick Encore

Excellent product, installed easily just like shown in the installation video. Kudos for having the installation videos available!!


Great people to work with, very helpful and polite would highly recommend

2018 Buick Encore

Very pleased with the merchandise I Purchased easy to install

2018 Buick Encore

Installing it was easy for me.


Was simple and easy to install. Company shipped it fast! Thank you!!


Easy to install and still working perfectly one year later.




Great price along with customer service! Received on time without and damage.


Arrived in a few days. Easy to install (20min)





very helpful and fast shipping



fast processing and shipping, good pric es.



2020 Buick Encore


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

  • Draw-Tite Hitch for Mototcycle Towing With 2018 Buick Encore
    The Draw-Tite Class II hitch # 36554 is rated for 300 lb tongue weight and 3,500 lbs towing, most small utility/motorcycle trailers and one dirt bike would be less than this max range; please reference your trailer and motorcycles weight for an accurate assessment. I highly recommend that you refer to your specific vehicle's owners manual prior to towing. My research, the online manual I have available (Part No. 84098804 B Second Printing), has a statement on p197 "The vehicle is neither...
    view full answer...
  • What Wiring Harness will Fit My 2021 Buick Encore GX?
    As far as wiring, if you need just brake lights/signal lights alone on your 2021 Buick Encore GX, you will only need the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118745. The T-One includes a ModuLite power converter to ensure that your vehicle's wiring matches that of your trailer. If you are looking to add a brake controller to the trailer, you will need the Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat # ETBC7 in addition to...
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  • Parts Needed to Transport 2 Dirt Bikes with a 2017 Buick Encore
    If you're talking about BMX dirt racing bikes then I recommend using the Draw-Tite Class II Trailer Hitch # 36554 on your 2017 Buick Encore with a bike rack like the Saris Freedom # SA4412B to get the job done. If you're wanting to transport actual dirt bikes then you're going to need to add the T-One Wiring Kit # 118745 and a ball mount kit like part # 36061 with a 1-7/8" # 19257 or a 2" # 19258 hitch ball so that you can load the bikes up into a trailer. The reason you'll need to go...
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  • Parts Needed To Install a Trailer Hitch Receiver and 4-Way Wiring On a 2019 Buick Encore
    For your 2019 Buick Encore I recommend the Draw-Tite Trailer Hitch Receiver # 36554. This is a class II, 1-1/4" receiver that is rated for up to 300lbs of tongue weight and a towing capacity up to 3,500lbs. Be sure to verify your maximum capacities with Buick and do not exceed the lower of the 2 ratings. Draw-Tite recommends the Drawbar # 36061 with either a 2" HItch Ball # 19258 or 1-7/8" Hitch Ball # 19257. The Tekonsha T-One Vehicle Wiring Harness # 118745 will provide you a 4-way...
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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Joshua S
Video by:
Joshua S
Employee Zach D
Video by:
Zach D
Employee Jonathan Y
Video by:
Jonathan Y
Employee Dustin K
Video Edited:
Dustin K
Employee Chris R
Video Edited:
Chris R
Employee Cole B
Installed by:
Cole B
Employee Alexander C
Written by:
Alexander C
Employee Shane H
Test Fit:
Shane H
Employee Ryan G
Test Fit:
Ryan G
Employee Clayton O
Test Fit:
Clayton O

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