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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 # 118798
Our Price: $50.55
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Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Powered Converter 118798
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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. 1-636-306-4830 to order Tekonsha custom fit vehicle wiring part number 118798 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 - 118798

  • 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 in rear cargo area
    • Plug in T-connector
    • Run hot lead to car battery
  • 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


  • Maximum amperage:
    • Stop/turn lights: 5 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 temporarily remove the rear threshold plate and partially remove the felt trunk liner 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.

118798 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

This Product Fits The Following Vehicles

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 T-One Vehicle Wiring Harness Installation - 2022 Toyota Avalon

Hey everybody, how's it going Today we're gonna be going over and showing you how to install the Tekonsha T-One Trailer Wiring Harness here on our 2022 Toyota Avalon. So a trailer wiring harness is gonna be one of the many things that we need in order to tow a trailer with our Avalon. In addition to this, we're gonna need a trailer hitch and a ball mount slash hitch ball, all of which we carry here at etrailer. Now what the trailer wiring harness actually does is it's gonna transmit the vehicles' taillight signals to the trailer, which is a legal requirement in every state. A lot of your larger camping trailers are actually gonna cover the taillights on the vehicle, so we need a way to safely transmit those signals so we can arrive to our destination safe and sound. So when we're not using our trailer wiring harness, it's actually gonna be stored in the trunk here which is really great for those people who aren't towing every day.

We wanna keep that trailer connector protected because if any water gets on the pins there they could corrode and cause trailer lighting issues which is not something we want. But when it is, when we are ready to use our harness, it is super easy. All we do is open the trunk, take the trailer connector and then drape it out through the hatch here like so, and then we're gonna close the hatch here on the trailer connector. There's a nice little rubber seal here, so you're not gonna pinch the wires. Close that and now we can easily hook up our trailer.

Now, if you're absolutely against this, I completely understand. There is a grommet in the bottom of the vehicle there that we could cut the wires, route it through that grommet and then probably secure it to the hitch underneath. But again, I really don't recommend that. Chances are with your Avalon here, you're not gonna be towing every day therefore having it protected inside the vehicle is gonna be the best spot for this. So our kit here is gonna provide us with a most common and widely used type of trailer connector.

That's gonna be called a four way or also known as a 4-pole flat and this is going to transfer all the basic signals that we need such as the stop and turn signal circuits for either side, as well as the running lights. We also have a dust cap here. Should you decide to route it outside the vehicle, we can still protect it a little bit although it's not gonna be as good as just keeping it inside the vehicle. So this is a protected module kit and basically what that means is you're not pulling power from the vehicle's taillight circuits for the trailer. You're actually pulling power directly from the battery.

So you're not gonna create any additional strain on the vehicle's electronics. It's gonna keep everything nice and separated. So issues with the trailer don't affect your vehicle. So in regards to installation, this is a pretty straightforward kit. I would definitely say this is probably one of the more easier trailer wiring harnesses to install. There's no splicing or cutting into wires whatsoever on the vehicle. The bulk of your install time is just gonna be routing the power wire from the rear to the front of the vehicle. I know people don't like doing that, but it is necessary. It's just gonna take you a little bit of time. I would say, give yourselves around one, two hours to complete this job, but we'll actually walk you through this entire process step by step now. So first step of our installation, we need to open up our hatch here and we're gonna be removing this threshold panel. Now there's a couple different fasteners holding this threshold panel in place. We're gonna start by removing these plastic pusher bits here. So just pry out that center section. The rest of it should follow. We have one here and then we have one over here. So next we're gonna have a cargo hook here on either side at the top. In order to remove these, there's a center section you're gonna press in then you should be able to pry them out. And now finally, we have one more little pop rivet on either side here. So same one as the one to remove down below but this one's up a little bit higher. Just pry out that center section and the rest will come out. And now with our fasteners removed, we should be able to lift up and out on our panel. Now we're gonna be pulling back the felt liner here to reveal the back of the taillights. Before you do that, you wanna make sure you remove this little push fastener up there and then we should be able to pull away enough to gain access to our taillight plug behind here. So now we're gonna separate the taillight connectors. We're working over here on the driver's side just as a point of reference but it doesn't matter which you start with. So if you pull back that tilt, that fabric liner here, you can see the plug coming from the back of our taillight. And if we follow that all the way to the wire this is our taillight connector here. And on the outside of that connector there's gonna be a little tab, it's kind of hard to see but you're gonna press that and then you're gonna pull up on your wiring harness there to separate the connectors. Now we'll take our wiring harness here that comes in your kit, we're gonna grab the connectors with the yellow wire going to them, and I'm just gonna simply plug them in between the ones we just removed. So now we're gonna take our two connectors here with the red wire, I'm gonna route that over here to the passenger side and just repeat those same few steps here. So your connector should only go in one way so you don't have to worry about that. There we go. So next we're gonna be securing the ground coming from our converter. So there's actually a factory ground here, which is great. We don't have to drill into the bodies. So we're just gonna take a 10 millimeter socket, remove that. So then we'll just place our ground over that bolt and then resecure it like so, super easy. So next we're going to secure our converter box in your kit. We're gonna get some double sided tape, just place it on the back of the converter box and then I think if I lift up this panel here I should just be able to sneak it down and just attach it to a part of that corrugated metal that sticks up there. Make sure we hold it there for a couple seconds so it's nice and tight. So now the next thing we need to do is we're gonna take the black wire coming from our converter box, this is for our power wire. We're gonna place all the butt connector that comes in your kit, I'm gonna crimp that on, and then I'm gonna take the power wire that comes in your kit and I'm gonna strip some of the jacket off that, I'm sure you probably guessed it. We're gonna attach this to the other end of our butt connector. And once we get that crimped on there we're gonna take the other end of our wire, we're gonna find some sort of grommet in the bottom of the vehicle, that way I can route this up to the front of the vehicle where our battery is. So now we went ahead and found a grommet here and the one I think we're gonna use, if you just remove this little floor covering it's gonna be the one all the way back here. So all I'm going to do is I'm just gonna take a razor knife, and I'm just gonna cut a small little hole there in the center of that grommet, that way I can just feed my wire down through there. So the goal is to do this without pushing the grommet back underneath the vehicle. There we go. But we also want a nice and tight seal, that way we don't have any water getting in the cab or anything. So now that we have our power wire routed underneath the vehicle, our four pole connector here is actually just gonna live inside the vehicle. You can choose to store this over the panel here or you can choose to store it sort of in here. There's actually a nice little puby there I kinda like, so I'm just gonna tuck it down in there but we're pretty much finished inside the vehicle here. So I'm just gonna go ahead and reinstall everything that we removed previously. So now we're gonna come underneath our vehicle here. We're gonna take our power wire and I'm gonna route this from the rear of the vehicle all the way to the front to where our battery is. Now you wanna be careful when you're routing this wire here cuz you wanna make sure you avoid any of the moving suspension components or any heated components such as the exhaust. We're gonna go ahead and do that now, and then we'll show you the path that we took. So your wire's gonna come down about this area here. So all we did is we went up and over the cross member section here and then it's actually gonna come back down behind this panel here. You can actually see it, the wire. And basically we're just gonna route this. There's a lot of underbody panelings on this vehicle. So we're just gonna route the wire over that. I took a socket there and I removed these plastic nuts. You actually just need to loosen them a little bit so you can pull this panel down. And then I just tucked our wire behind that there just to keep it from coming over here to where our exhaust is and then it's pretty much just routed. Above this panel here, same thing. We have another fastener here, I just ran it behind that. Same thing for this one. This one actually takes a flathead though, once you remove that. They don't actually come all the way out, they just come down and then I just wrapped the wire on the other side of the stud and I'm gonna come all the way down here to where our wire comes out here. I went ahead and took a zip tie just secured it to the brake lines here, because we do have our exhaust right here, gets super hot, so we wanna make sure we avoid that as much as possible but now we're gonna show you how to get the wire from here up into the engine bay. So now we're up in our engine bay here. I'm gonna be over here on the driver's side where our battery is. I'm gonna take a piece of airline tubing or a plum bob which is basically just a nut with a screen tied to it. I'm just gonna feed it down into the engine bay as best we can. Basically, I want this to come out underneath there, so when I get back underneath the vehicle I can reach up there, pull this out, tie my wire to it and then pull it back up into the engine bay. I'm just securing it up here, that way I don't pull the airline tubing back through there when I go underneath and grab it. So here is our pole wire. It was just right up there, so I just reached up there, grabbed that and now I'm gonna tape my power wire to that pole wire. It's really best if you use electrical tape for this because it's got some flexibility there. It won't just tear on you. Here we go, that should do it. So now I'm gonna go back up top there. I'm gonna pull that pole wire through and that's gonna bring our wire up into the engine bay. And I will probably come back down here again once I have all that slack up there. I'm gonna put another zip tie on my brake line here because I have the catalytic converter right here which gets very, very hot. So we wanna make sure that wire is as far away from that as possible. So there's our wire. And now that I have it into the engine bay here I think I'm gonna take another zip tie and just secure it up here, that way I don't have to worry about it falling back down. So here's where we got our wire routed here. There's plenty of extra, so I went ahead and cut a lot of that off but what we are working with here, just gonna go ahead strip some of the jacket and then I'm gonna attach our fuse holder. Now your fuse holder doesn't come like this in the kit. It comes as a loop. You're gonna need to cut that. Attach a butt connector to one end and a ring terminal to the other and then we'll just simply attach the other end of the butt connector to our bare wire. Once we have that done, we're ready to attach it to the positive battery terminal. So just go ahead and remove this cover here like that. Then we're gonna take a 12 millimeter socket and remove that bolt there. Once I have that out I'm going to secure my ring terminal to that stud there and just simply resecure the nut. Now what we can do is, we'll take our blue fuse and we'll insert it into the fuse holder. And pretty much the only thing left to do there is just resecure our cover there for the positive battery terminal. You may need to make a small notch in there to allow the wire to pass through but aside from that ready to test. So now to test everything out, we're gonna be plugging in a little four pole tester. You can pick one of these up here at etrailer if you want but I would probably just use your trailer if we're you. Keep that in mind though, that if you do use your trailer any issues with the trailer could carry over to our testing on the vehicle but that being said, go ahead, run through our signals now, got our brakes, left turn, right turn and finally our running lights. So now that everything is working correctly that's gonna do it today for our looking installation at the Tekonsha T1 Trailer Wiring Harness here on our 2022 Toyota Avalon..

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118798

Average Customer Rating:  5.0 out of 5 stars   (1 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.

2019 Toyota Avalon

The trailer hitch looks great on my new Toyota Avalon. It fits great.


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

  • Which Hitch for 2021 Toyota Avalon Has Most Ground Clearance
    Between the two hitches available for a 2021 Toyota Avalon, the Draw-Tite # 36643 and the Curt # C11576, the Curt # C11576 would provide about 1/2 inch greater ground clearance. Also, the Curt hitch would have the crossbar concealed behind the vehicle's bumper with only the receiver tube and safety chain loops being visible. The Draw-Tite would be entirely visible from the rear with the crossbar sitting directly below the bumper fascia. Both hitches will fit Hybrid models. Because of...
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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Installed by:
Kathleen M
Employee Wilson B
Updated by:
Wilson B
Employee Alexander C
Written by:
Alexander C
Employee Conner L
Test Fit:
Conner L
Employee Thomas T
Video by:
Thomas T

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