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

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

Item # 118585

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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 118585
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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. Call 800-298-8924 to order Tekonsha custom fit vehicle wiring part number 118585 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 (15)
  • Q & A (6)
  • Videos (2)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118585

  • 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. 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
    • 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: 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 behind the driver's-side and passenger's-side tail lights. You will have to remove the tail light assemblies to access this harness.

T-One Connection Location Points Behind Tail Lights

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 connector will be stowed within the jack storage compartment of your 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.

118585 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

118585 Installation InstructionsInstallation Details 118585 Installation instructions

This Product Fits The Following Vehicles

2010 - 2013 Ford Transit Connect

2010 - 2013 Ford Transit Connect

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 Trailer Wiring Harness Installation - 2012 Ford Transit Connect

Today on our 2012 Ford Transit Connect, we're gonna be taking a look at the Tekonsha T-One Vehicle Wiring Harness, part number 118585. It's gonna have a 4-pole flat trailer end connector. It does come with a dust cover and it is gonna stay on the outside of the vehicle at all times. So, it's gonna be ready whenever we need our wiring. To begin our installation, we're gonna need to open up our rear doors so that we can gain access to remove the taillights. To remove our taillights, we have two plastic rotating clips.

Now, these may be pretty tight so we just take a pair of slip joint pliers or anything to grab them. We're gonna loosen them up and then remove them by hand the rest of the way. And once those are removed, if we look inside of here, we're gonna have a 10 millimeter nut, so you're gonna need a 10 millimeter deep well socket and we're gonna remove those bolts. With those bolts removed, we can come to the outside of our taillight and we're just gonna grab out taillight and we're gonna pull straight back. So, we're gonna unplug our vehicle's wire and harness from our taillight. There's a tab right here.

If you push on this tab, it'll release the taillight, and we're gonna do the same thing on the other side. And we're gonna set these aside so they don't get damaged or lost. Next, I want to bring your attention to our wiring harness. You might have noticed that there's some connectors between the wires, but not on the yellow end. Well, for now, we're gonna disconnect our red and green ends and we're gonna set the connectors aside and we're disconnecting our 4-pole end with the green, yellow, white, and brown wires.

We're gonna set this aside for installation later. If we come over to our driver's side, we're gonna be taking the yellow, brown, and white connector, and we're gonna be plugging it in the vehicle's end. We want to make sure that locks in and we're gonna move back to the inside now. Right above our hinge, there's gonna be a plug. We're gonna need to remove this plug, so we can gain access to our wires. And I'm simply gonna use a screwdriver and a pair of pliers to grab it.

We're gonna do the same thing on the other side. On the outside, where our taillight was, this hole right here is where we just removed that plug and now we're gonna need to feed through our green and red wires, as well as the 4-pole wires. The green, yellow, white, and brown. And you're gonna want to do this one at a time. Get the connector through and a little bit of the wire so that you'll have enough room to get the following wires through. Once we have enough room, we're gonna pull it through and then we can come back and put our other wires and connectors through. Now, it is gonna be a snug fit but it will work. And we're gonna come to the other side and make sure everything's feeding properly and getting through. Now, there is one more wire that we're gonna need to put through and that's gonna be our black wire. I'm just gonna push that through to the other side. Now, the only remaining wire is gonna be our T connector and our ground. Now, this ground, I'm simply just gonna loosen this bolt right here and use it on the factory existing ground. I'm gonna use an eight millimeter socket to remove this bolt. With the bolt removed, put my ground wire on and then reinstall my bolt. I'm gonna be attaching the supplied black wire. The kit does come with butt connectors, but since this is more towards the outside of the vehicle where it's gonna come in contact with some moisture and maybe dirt, I'm gonna replacing the supplied butt connector with a heat shrink butt connector and you can pick those up on our website using part number DW05745-5. You'll need to strip the end off of this wire, then I can take our butt connector and attach it to this end, and then I can take the other end of the black wire, insert it in the other end and crimp it down. And you can use any heat source to apply the heat shrink on this butt connector, but we're gonna be using a heat gun. You just want to double-check and make sure you're not gonna char or burn the wire or the connector itself. Now that we have our black charge wire connected, I'm go ahead and reconnect our 4-pole end and we're just gonna match up the colored wires going to each other. Now, with all of our wires connected, we're gonna take all of our wires and we're gonna go down right here, just on the outside of this weather stripping. Right behind the bumper right here. So, we're just gonna start feeding all of our wires down and once we get all of them started, we're gonna need to go underneath the vehicle and pull them out. Now, before we run our wire, I'm gonna go ahead and connect our red and green T connector to our passenger side. That way we can feed our wires down through the same hole that we took that plug out and we can meet up with our wires from the other side. Now, we're gonna come back to our driver's side under the vehicle and we're gonna take our red and green wire and we're gonna run it along the edge of the bumper here behind it and come back and connect to our other end of our connector. When you come to the back of the bumper, behind it here, there's a panel that's gonna be like a support. If you go behind it, it is gonna help it rubbing on the exhaust or the hitch or anything else, just to give us that little bit of extra security before we zip tie anything down. The wires come out right above the bottom of the bumper. Now, luckily, our connectors have a male and a female end. So, if we just match the female with the male end and the male with the female end, it'll be on the right connector. So, you can just reach up and connect our connectors and for now we're gonna leave this wire and we'll tidy it up later. Our black wire, we're gonna need to run this up to the vehicle's battery. Give me a few minutes and I'm gonna run it and I'll show you how I get it done. Now, everybody is gonna run it a little bit differently. So, let me show you how I ran my wire. This is where it came out, I went up, zip-tied it to a factory wire here, came across, tied into my factory ABS wire, came down, attached to my emergency brake cable, zip tying it along the way, and I jumped over to the outer edge of the frame. There's a small loop right here, so I zip tied it there as well. Then came back to the center section of the frame and zip tied it here and finally it stops right here and we're gonna go up to the top underneath the hood so we can run this to the battery. Okay, now, we're gonna have our wire coming up to positive end of our battery here. So, I've got some airline tubing that I had lying around and I'm gonna be routing this down and coming out so we can attach our wire and pull it back through. Now, you can use anything if you don't have airline tube. Basically, anything that's gonna hold it's shape so that when you push it down through it can get all the way through to the bottom. So, here's where our airline tube came out. I'm gonna take the end of our wire. I'm gonna insert it into my airline tube. Just gonna use a little bit of tape to secure it. We can go ahead and pull our wire up. Then we can disconnect our airline tube. Next, we're gonna need to attach our fuse holder to the end of our wire. So, we're gonna take our wire and we're gonna strip the end of the wire off. We're gonna take another one of our heat shrink butt connectors and crimp it on to the end of our black wire. Now, we can take our fuse holder. We're gonna cut the wire so we have a nice end on each side and we're gonna strip one end of the wire, and we're gonna attach it to the other end of our butt connector. Now, on the other end of our fuse holder, we're gonna strip that end of the wire as well and we're gonna be putting on the ring terminal that is supplied with the kit. Now, we're gonna take our ring terminal and we're gonna move the positive side posts for our battery terminal and we're gonna attach it there and I'm gonna be using a 10 millimeter socket to remove the nut. Then we're just gonna remove the nut, put our terminal on, and then reinstall the nut. We do have all this excess wire, so I'm just gonna tidy it up and zip tie it right here. That way if any repairs are needed, we'll have that extra wire. Now, if we come back to our taillight here where our module box is, I'm gonna take the provided double-sided tape. Take one side off, put it on the box. I'm gonna take the other side and I'm gonna put this box as far down in the taillight channel as I can and then push it firmly into place so it'll hold against the body of the vehicle. Plug them in and then we're gonna reassemble our taillight. After we have inaudible 00:12:06, we can come back and put our black rotating caps on and we'll go ahead and do the same thing on the other side. Now all we have left to do is tidy up our wires and run our 4-pole to the center where the hitch is and we can tie up any excess wires. Just gonna route our wire. I'm gonna take my dust cover. I can leave my 4-pole right here and I'm just gonna tie up this wire back here with a couple of zip ties. I'm just gonna coil up the excess wire, zip tie a bundle together, and then I can come back up to the bumper support channel and actually just tuck it up behind there. We still have access and we can pull any access if we need it. Now, with everything done, we can go ahead and put our fuse in and we can test our lights. And if you don't have a tester, you can pick one up on website using part number I26. Now, if I can have the running lights, please Okay. Can I have the brakes, please Brakes are working. Can I get a left turn signal Right turn signal Brakes and the turn signal The other turn signal All right. There we have it. We know all of our lights are working. And that'll finish up the look of the Tekonsha T-One Vehicle Wiring Harness, part number 118585 on our 2012 Ford Transit Connect.

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118585

Average Customer Rating:  4.9 out of 5 stars   (15 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.

- 118585

the hitch mounted very easy, with no problems. the wireing harness was put togeather in a complete packet, and very simple to enstall. we was able to put the small black box into the left rear light houseing for total wether protection, and spliced the two wires over to the right rear light housing unit. when finished, it looked very professional done. not so much on our part, but the quality of the products that you supplied sorry about not having any pics, they did,nt come out very good 234711

- 118585

Product shipped quickly and e-trailer agent James sent instructions on the install. EZ PZ. Thank you James. Everything works spot on. 650548

- 118585

Works well, fairly easy install. 641149

- 118585
2013 Ford Transit Connect

The harness works great! Easy to install, well documented. 502134

- 118585
2013 Ford Transit Connect

Good directions made it an easy, and fun DIY project. 491302

- 118585

Ordered mutiple hitches and wiring harnesses. All came quickly and installed without issue. Great service and pricing! 490450

- 118585

Super easy to install works great 451779

- 118585
2012 Ford Transit Connect

I am very happy with the wiring harness I purchased last year ! It has worked flawlessly and made my Transit connect a much more versatile vehicle ! Thank you for the follow up ! 445696

- 118585
Ford Transit Connect

Ordering the electrical harness was a good idea to go along with the etrailer hitch for my '11 Ford Transit Connect. If the green/red wire could be around 6-8" longer, it would then be easier to connect them on the rear passenger side bumper area. Other than that, very convenient. 443711

- 118585

HI, Its was an excellent experience to work with your company, best seller .thanks 429485

- 118585

Ordering was easy, package arrived on the day promised, product was right on the money and went on beautifully! Saved us about $300! We pulled a uhaul trailer from N. Ga to Central Florida on our new hitch and it was perfect! Thanks so much! 392804

- 118585
2010 Ford Transit Connect

Great product, easy to follow up installation instructions. Even a carpenter can do it!! Best way to power the system is around the car threshold under the covers. I don't believe a pro installer can do it better, very good product!! Cornel the carpenter 387440

- 118585
2012 Ford Transit Connect

Got this in Mail yesterday. Looks Great. Easy to install. Saved a lot of time. 385162

- 118585
2013 Ford Transit Connect

The trailer wiring harness for my 2013 transit connect was one of the more difficult hookups I have done. The most difficult step for me was running the power feed wire from the rear of the vehicle to the battery in the front. The harness it self was as advertised and plug and play. Most of the time consuming work was because of vehicle design not because of harness design. The instillation video was a life saver. shipping was quick and the product worked as advertised. 364680

- 118585

Was my first online purchase and am quite surprised of the quality of the service. My purchase was delivered way in advance of the anticipated delivery date. Will not hesitate to order from this again. 187978


Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

Do you have a question about this Custom Fit Vehicle Wiring?

  • Trailer Wiring Harness Options for a 2010 Ford Transit Connect
  • The Curt trailer wiring harness, # 56090, is a fit for a 2010 Ford Transit Connect. I have included a link to the installation instructions for you. If the vehicle came with a factory tow package, the correct wiring harness is # 118585. I have included a link to the installation instructions for this harness as well.
    view full answer...

  • Recommended 4-way and 7-way Trailer Connector For 2011 Ford Transit Connect
  • If you have no trailer connector on your 2011 Transit Connect, the first thing you will need is a 4-way connector. I recommend the T-One Vehicle Wiring Harness, part # 118585. This plugs into the vehicle wiring located behind the tail lights. You just plug this harness into the tail light wiring, then run the hot lead wire to the positive battery cable. Then to install a 7-way and 4-way trailer connector you will need part # ETBC7. This plugs into the 4-way connector. If you...
    view full answer...

  • Is Exhaust Lowered To Install Draw-Tite 75678 Class III Trailer Hitch on 2010 Ford Transit Connect
  • According to the installation instructions, lowering the exhaust isn't required during the installation of the Draw-Tite # 75678 on a 2010 Transit Connect. The instructions do call for the spare tire to be lowered to gain access to the frame and then raised back up into position after the install is complete. Installation of the Tekonsha Custom Fit Vehicle Wiring, part # 118585, is not too bad. The unit simply plugs into the factory connectors of the tail lights on each side of the...
    view full answer...

  • Comparing the Curt T-Connector 56090 and Tekonsha T-One 118585 for a 2010 Ford Transit Connect
  • The Curt T-Connector Vehicle Wiring Harness part # 56090 and the Tekonsha T-One Vehicle Wiring Harness part # 118585 are both fits for your 2010 Ford Transit Connect. They are essentially two different manufactures version of the same product. The purpose is the same as well as the install. The only difference is really in terms of quality and that edge goes to Tekonsha as we have less issues with the T-One than we do with the T-Connector but both will work just fine for you. I have...
    view full answer...

  • Does Curt 1-1/4 Inch Trailer Hitch Receiver C12076 Include the Ball Mount
  • No, the Curt Class II hitch receiver # C12076 does not include a ball mount, hitch pin or clip. You will need to add a hitch ball of appropriate size to match your trailer and a pin and clip # F-4. I have included a link to our page for Class II hitch balls with the required 3/4-inch shank diameter (to match the supplied ball mount which has a 3/4-inch ball hole). With this link you can select a Class II hitch ball of the appropriate size to match your trailer coupler, either 1-7/8 inch...
    view full answer...

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Info for this part was:

Written by:
Lindsey S
Expert Research:
Michael H
Expert Research:
Jeffrey L
Installed by:
Jeff D
Video Edited:
Joshua S
Video Edited:
Jacob T
Updated by:
Laura H
Updated by:
Sarah W
Updated by:
Alexander C
Updated by:
Isabelle B
Video by:
Chris R
Test Fit:
Robert C

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