1. Custom Fit Vehicle Wiring
  2. Tekonsha
  3. Custom Fit
  4. Trailer Hitch Wiring
  5. 4 Flat
  6. No Converter
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

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

Item # 118519
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Custom Fit Vehicle Wiring

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Tekonsha Custom Fit Vehicle Wiring - 118519
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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 118519 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 (13)
  • Q & A (7)
  • Videos (3)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118519

  • Custom Fit
  • Trailer Hitch Wiring
  • Tekonsha
  • 4 Flat
  • No 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 battery
  • Includes ModuLite to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects directly to the 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.

Tail Light T Connector Diagram

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 an out-of-the-way location within your cargo area. It is recommended that you use a small amout 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.

118519 Tow Ready T-One Vehicle Wiring Harness

Installation Details 118519 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 Trailer Wiring Harness Installation - 2014 Lincoln MKX

Today on this 2014 Lincoln MKX we're going to install part number 118519 from Tow Ready. First thing we need to do is go ahead and open the tailgate so we get access to the taillights. To remove our tail lights we got to remove these two screws here and there's two alignment pins up in the front, so we'll go ahead and pull our lights back. We'll use 8mm socket to remove these bolts. To disconnect our wire harness from our taillight we'll push down on this tab here and pull it apart. Set this to the side for now. Do the same thing on the passenger's side.

At this point we got the taillights removed, we'll go ahead and we need to remove our floor coverings . Our floor coverings out of the way, next we need to move is the threshold right here. Make sure the tire hooks are up and go ahead and pull straight up on the threshold to unsnap it. There it is. A steady pull and it pops up.

Next we need to go ahead and take out these pockets or wells that go around the spare tire. These wells, they have alignment pins but they just simply pull up. On our driver's side we have to go ahead and loosen up this grommet right here. You can grab it with some pliers and just gently pull it out. That will give us access from the inside to the outside. We'll do the same thing on the passenger's side.

It's going to be a tight fit on the backside behind here because there's a speaker box. We need to loosen up this panel and also the speaker box as well. We'll go ahead and remove this tie down point here. We can go ahead and peel this back a little bit. There will be some snaps that we'll have to remove.

For this you'll want a trim panel tool. Kind of reach in and find the snap, I think it's about right here. Pop it loose. It kind of goes around it, grips it and pops. One on top that came out on its own. Towards the bottom there's another plastic rivet we'll want to remove. Pop it up and out of the way. The other snaps will pop loose. Keep working it back and forth. Then we loosen up this screw here, and there's one way back here. This whole speaker assembly we can go ahead and move a little bit out of the way to run our wires through . Now you can see how we can move it, give us working room. Let's go get our wire harness out and we'll go ahead and start making connections. This t-connector to the green wire we ran behind our plastic and out to the passenger's side. Next we'll do the same thing with the t-connector with the yellow wire. We're just going to let that sit in there for now. Let's do the same thing on the driver's side. This one has considerable room to work with . So we don't have to take the panel off. We'll go ahead and cut it. I like to use the bottom edge of it, use some tin snips . Cut it just enough to run the wire through. Go ahead and put our wires through it. We can go ahead and reinstall the grommet . This is our factory wire harness. Well plug the matching end to it from the t-connector into it, and then this half will plug into the back of your taillight which we can go ahead and reinstall at this point anyway. Push it back in place and reinstall our two screws. Let's go ahead and do the same thing over on our passenger's side. Our t-connector will fit into the factory wire harness and this will go into the taillight. At this point, we can go ahead and put our interior panel back together . We'll go ahead and tuck our green wire underneath our plastic here. We'll stay on the inside edge for when we put our cover back into place it will keep it from falling down. I'm going to use some packing tape to help hold it in place while I put the threshold down too. This way we don't have to worry about our wire being pinched anywhere it doesn't need to be. One last check and pop it into place.Next we'll go ahead and work from our module. That's this box right here. This will plug into this gray connector. We're going to use adhesive right here to attach to the sheet metal on the floor underneath our plastic. We'll go ahead and clean it off first . Nice clean sheet metal . Well attach it. Next we'll go ahead hook up, white wire the ring terminal. We'll attach that to the sheet metal on the floor as well. There's some places here where you can see these weld marks, there's two pieces of material there so we'll go ahead and attach it to that. We'll use the self-snapping tool that comes with the kit and I'll use a quarter inch nut driver. Next we're going to route our full pull to this grommet right here. We're going to pull it up and make a cut in it just like we did before behind our taillight . Well go ahead and take our full pull and ride it on through. This is actually sitting on top of the heat shield right now. We'll go ahead run the wire through the cut, put our grommet back in place. Next we'll go ahead and work with our black wire that comes with the kit. It's going to connect up to the wire harness with the yellow butt connector. This will eventually be ran to our 12 volt power supply. We'll strip this back and add to our butt connector . We're going to run this out the bottom of the vehicle and up towards the front, except we're going to use this grommet instead. This gets us past the majority of the rear suspension all the way up towards the front. This will be kind of easy. Let's just poke a hole in it with a screwdriver and we'll take the wire and sneak it underneath the plastic and then go through the grommet.We'll use a trim panel tool to pop up these rivets and just slide our wire underneath of it. Let's go ahead and just thread it through here, then down through our grommet . Now we're done with routing all the wires on the inside of the vehicle, so at this point we can go ahead and reinstall our interior components. Then we'll go ahead and continue with our full pull wire harness and our black wire underneath the vehicle. Lets go ahead and take our full pull wire, pull it out . Make sure we get all our slack out. Our previously installed hitch has a mount for a bracket. We can use a bracket to hold our full pull in place. We'll be using part number 18144 from Tow Ready. We'll use the small screws that come with the bracket to connect the two together, two screws and two nuts, built in star washer. We'll tighten these down with the 3/8th socket.The full pull itself will go through the bracket and friction fit, kind of work it past to hit the built in ridge and go ahead and put the cap on. Then we'll go ahead and take our excess wire, we'll tuck it up back on top of the hitch. Next we'll look for a wire that will go toward the front. About this location right here above the rear suspension, is our grommet. We'll go ahead and show you how we route our wires. As soon as we got past the rear suspension, across some factory wiring, went around the gas tank, zip tied it in places where we could . We went ahead and came back up to the parking brake cable here. We unbolted this panel and pulled it down and routed it through some empty brackets here and just followed some lines going up towards the top and then zip tied along the way. We'll go ahead and put our panel up and bolt through with an 8mm socket. We're going to use a pull wire to route this wire up towards the top and towards the 12 volt power supply . Once we have the full wire ran down from the top to the bottom, we'll go ahead and attach it to our black wire here. We'll go ahead and just pull it back up. I'm going to route my wire up and around following the ground cables behind our fuse panel, then up to our 12 volt supply right here. We'll go ahead and figure out how much length we need and we'll cut off the excess. We'll zip tie our wire. At the end of our black wire we'll go ahead and add our fuse holder. We'll go ahead and strip the wire back. We'll go ahead and put a cut in the loop. One end will get a ring terminal and the other end will get a butt connector that Ill connect to the black wire .Since this butt connector's going to be outside, I'm going to add a little extra protection to it with some electrical tape. We'll add it to our power supply at this point right here . We'll put our cover back on and we'll add a fuse to the fuse holder. We'll use a 15 amp fuse that comes with the kit . Tuck that back down beside the battery here, and a fuse box, and we'll be good to go. Easy access to it in case we ever have to change it. With all of our electrical connections made, we'll go ahead and test our wire harness to make sure it's working before we try it on our trailer. Let's go ahead and test or wire harness. We'll take our ground clamp and go to the white wire, and then we'll test the ground wire for running light circuit. Then we'll try our left turn signal and now our right turn signal, and our brake signal will be a constant signal on both wires. It looks like everything works. Now I think it's a good time to try it on our trailer. With that, that will finish it for our install with part number 118519 from Tow Ready. This is a T1 vehicle wiring harness on our 2014 Lincoln MKX. .

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118519

Average Customer Rating:  5.0 out of 5 stars   (13 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.

- 118519

One year after purchasing and installing the Tenosha Wiring Harness, I can proudly report the equipment has met my every expectation. As with any purchase made from etrailer, I am very happy with my purchase. 720447

- 118519
2012 Lincoln MKX

Fast delivery and quality product 696238

- 118519
2012 Lincoln MKX

Got my wiring kit quickly as usual frokm etrailer. Installation instructions were spot on and made the install super easy. The hard part for me was running the power wire from the back to the front of the vehicle underneath and keeping it away from things that might damage it or cause a fire. I wonder why they don't let you fuse it to a power outlet wire in the hatch area but that is a manufacturer issue. 666279

Thats a great question, and one we get frequently. Drawing the power directly from the battery serves to isolate the vehicles sensitive, complex and expensive to repair electrical system from any short circuits that may occur in the trailer wiring.
-- Mike L - 07/05/2019


- 118519

Every thing went according to plan. Hitch and wiring came in a timely manner. Thanks 643914

- 118519

Delivered on time . Install was easy with install video. 617644

- 118519
2013 Lincoln MKX

Same part number as Draw Tite and no cross reference needed. I purchased this part $35 cheaper than I could get from my own wholesale supply company. etrailer shipped lighting fast. Part is exactly as specified. 511358

- 118519
2015 Lincoln MKX

Great installation videos! Made installation go a lot quicker. Very easy to install. Product seems to be very durable. Good heavy gauge wire going from the battery to the controller. More than enough zip ties provided with it to secure the power line appropriately. 505382

- 118519

Great product great service everything went absolutely perfect thanks to all involved 461688

- 118519

This hitch is a quality product and is easy to install. The videos are extremely helpful. I know where I will buy my next hitch! 401462

- 118519
2014 Lincoln MKX

Excellent transaction. Thank you. 252978

- 118519
2011 Lincoln MKX

Ordering was easy. Item description was detailed. Install videos on youtube from etrailer made install very easy and efficient. Definitely recommend. 213465

- 118519
2008 Ford Edge

Easy install and hookup with simple hand tools. Highly recommend these kits. Have used one before on an 08 Edge for nearly 5 years with no issues. 183535

- 118519

Received my order in just 4 days which was great. Will order again from etrailer if I need more. Watched the installation videos which were a great help and was able to install trailer hitch receiver in about 1 hour by my self 122854


Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Trailer Hitch and Wiring for a 2013 Lincoln MKX
    Starting with a trailer hitch you can use Draw-Tite Class III hitch # 75992 on your 2013 Lincoln MKX. This hitch has a 2 inch receiver and is rated for 400 pounds tongue weight and 4,000 pounds gross trailer weight. I have included a link to the installation instructions for you. For wiring you will not have to splice into the vehicle's wiring at all. The wiring harnesses for your vehicle plug in line with the tail light wiring. I recommend Tow Ready harness # 118519 because the tow...
    view full answer...
  • Availability of a 4-Flat and 5-Flat Wiring Harness to Power an Air Compressor on a Trailer
    With the set up on your 2013 Lincoln MKX, you best option will be to install the T-One Vehicle Wiring Harness, # 118519, and then use the Tow Ready 4 Pole to 5 Pole Wiring Adapter, # 20036. This the adapter will connect your 4 pole vehicle plug and 5 pole plug on your trailer. The trailer lights will be connected to your vehicle. The extra wire then can be wired up to the battery to power your air compressor. Depending on the amp draw of your compressor, I also recommend you wire in...
    view full answer...
  • Troubleshooting Factory Trailer Wiring on a 2011 Lincoln MKX, No Blinkers
    Sounds like you have a blown fuse or relay under the hood of your 2011 Lincoln MKX. Grab your owners manual and look up the fuse box legend. There should be a section that has tow package wiring. Check and replace those fuses as necessary. It also would be a good idea to check out the wiring of your trailer. There might be shorts on the turn signal circuits that caused the fuse to blow.
    view full answer...
  • Is Tow Ready No-Drill Mount Bracket Required for Mounting 4-Way Connector to Hitch
    When used along with the Tow Ready Mounting Bracket # 18144, the No-Drill Mount Bracket # 18140 you referenced will provide a nice bracket for your Tekonsha 4-Way harness connector # 118519 that won't require any drilling into the Draw-Tite Hitch # 75992. The No-Drill Bracket is not absolutely necessary, but it is what we typically recommend to avoid drilling into your brand new hitch or bumper. I have attached a short video demonstration so you can see exactly how this is used.
    view full answer...
  • Parts Needed to Add a 7-Way Trailer Connector and Brake Controller on a 2013 Lincoln MKX
    In order to add a 7-Way trailer connector to your 2013 Lincoln MKX you will need to hardwire one in. First, you would need to install a 4-Way using # 118519. I have linked a video showing an example installation for you. Then you can use installation kit # ETBC7 to add a 7-Way. I have included some links that show and explain the ETBC7 installation for you. If you tow a trailer with electric brakes then you will also need a brake controller. I recommend the P2 # 90885 because it is...
    view full answer...
  • Trailer Wiring Harness Options for a 2011 Lincoln MKX
    Curt trailer wiring harness # C56121 does indeed fit your 2011 Lincoln MKX. Installation will be the same as the video I have linked which features a 2013 MKX. We also have Tekonsha harness # 118519 or Hopkins harness # HM11140314 which also fit your MKX. They all install and function in the same manner but we do hear about fewer issues with the Tekonsha harness.
    view full answer...
  • Trailer Hitch and Wiring Recommendation for 2014 Lincoln MKX AWD
    For your 2014 Lincoln MKX the hitch I recommend is the etrailer hitch part # e98870 as this is a USA made hitch with more than enough capacity for your vehicle, is priced great, and only has the hitch opening hanging below the rear bumper which means it's mostly out of plain sight. The best trailer wiring option is the Tekonsha kit part # 118519 because it's easy to install and comes with a very reliable converter box. I attached an install video for this kit for you to check out as...
    view full answer...

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Info for this part was:

Test Fit:
Joe V
Test Fit:
Ryan G
Video by:
Andrew K
Video by:
Joshua S
Expert Research:
Michael H
Updated by:
Adele M
Updated by:
Laura H
Updated by:
Sarah W
Updated by:
Alexander C
Updated by:
Isabelle B
Installed by:
Cole B
Video Edited:
Chris R

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