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

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

Item # C56351
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Quickly and easily install a 4-way trailer connector on your vehicle with this custom harness. T-connector plugs directly into existing wiring. Powered converter reduces strain on wiring system and is made using SMT to ensure superior performance. 1-833-496-1390 to order CURT custom fit vehicle wiring part number C56351 or order online at Free expert support on all CURT products. Guaranteed Lowest Price and Fastest Shipping for Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
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  • Reviews (50)
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CURT Custom Fit Vehicle Wiring - C56351

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • Powered Converter
  • CURT

Quickly and easily install a 4-way trailer connector on your vehicle with this custom harness. T-connector plugs directly into existing wiring. Powered converter reduces strain on wiring system and is made using SMT to ensure superior performance.


  • 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 a powered tail light converter that connects directly to your battery to avoid overloading your vehicle's electrical system
  • Constructed using surface-mount technology (SMT) for consistent, reliable performance
    • Maximizes trailer light yield and intensity while producing minimal heat
    • Ensures superior operation in rough road conditions
  • 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
  • Limited 1-year warranty


This custom-fit T-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 trunk floor coverings, rear scuff panel, and tail light assemblies 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.

Once installation is complete, the 4-way connector will be stowed in an out-of-the-way location within 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.

Powered Tail Light Converter with Surface-Mount Technology

A tail light converter is built into this T-connector. This converter is a circuit-protected, battery-powered unit that bypasses the electrical routes that are used by a basic wiring harness. As a result, there is virtually no draw on your tail light circuits.

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 the trailer. This converter combines 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.

Curt builds each tail light converter using surface-mount technology (SMT). This method of construction involves soldering electronic components directly to the surface of a printed circuit board. SMT eliminates the need for leads, which are used in older through-hole technology. The result is a circuit board that is smaller yet provides more routing area and that offers superior performance, reliability and durability.

Curt SMT Circuit Boards

Circuit boards constructed using SMT have been shown to perform better under rough conditions with excessive vibration than those made using the through-hole method. And where would vibration be more likely to occur than in towing applications? Curt converters also produce less heat, leading to increased durability and longer life. In addition, lower levels of resistance ensure better performance, especially for parts that operate at higher frequencies.

Each Curt circuit board is made using high-quality components that are pieced together in the most technologically savvy fashion, leading to greater predictability and reliability in functioning.

56351 CURT T-Connector Vehicle Wiring Harness with 4 Pole Trailer Connector

Replaces 56178

Installation Details C56351 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Reviews

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - C56351

Average Customer Rating:  4.8 out of 5 stars   (50 Customer Reviews)

Quickly and easily install a 4-way trailer connector on your vehicle with this custom harness. T-connector plugs directly into existing wiring. Powered converter reduces strain on wiring system and is made using SMT to ensure superior performance.


Harness works great. Hardest part was running the power wire to the front with no access to a lift. No issues after a year of use. The installation videos will walk you step by step on how to install it right.

2015 Ford Fusion

I think the way people installing the wireing is crazy. One guy says he took off the rear bumper , to install the wires thru the large grommet. When you take off the rear light lens, there a small hole with a rubber plug, pop that out and run your wires thru it. You have to cut the wires and reconnect it.

2014 Ford Fusion

Everything included in kit you need to install. My only issue was installing wiring to taillights. I found it easier to remove bumper to ease routing of those wires through grommet to taillights. With hitch installed it is only a couple clips and screws holding it on. This made it easier for me and my big hands!

Still working great. Towed a utility trailer a few times with zero issues.
Eric N - 11/16/2018


Only used it a handful of time but was easy to install and has worked so far


Had someone else install.


Perfect fit. Was not able to use the plastic cover after mounting hitch.


Failed in less than 3 months.

You mentioned that it failed within 3 months and I wanted to ask you a few follow up questions. Can you be more specific in how it failed? I know that you replaced it however do you still have it?
-- Etrailer Expert Jenny N - 06/28/2022
The black converter box or whatever it is called failed. The lights no longer worked. They just stayed on dim. When I bought the new kit, to save time I only swapped out the black box as all the other connections were basically the same. It is still working fine. I do not still have it.
-- comment by: Frank - 06/28/2022

2019 Ford Fusion

I was impressed that you provided everything, including extra wire ties and a simple way (2-way sticky pad) to mount the controller. I was installing on a 2019 Ford Fusion Energi and there was not much space to pull the connectors through. I strongly recommend anyone doing this view the YouTube video from Uhaul. That video was very helpful.

2016 Ford Fusion

Pretty easy to install. I have a hybrid, so the battery is in the truck near the driver's side taillight. That really simplified the install. The video showed them snaking a tube up through the grommet hole. I found it easier to drop the connectors down to the ground from inside the trunk, then run a fish tape down from the taillight housing. Tape the two together then pull up and into the housing. I also did the passenger side first, so I would have as much slack as possible by moving the module all the way over to the left.


It functions as described, but the install effort isn't worth the trouble versus directly tapping to the to harness in the trunk rather than at the tail lights. Feeding the connectors through the fender to the tail light locations goes through a circuitous route with very tight fit. Especially the left side with two connectors. Misleading instructions aggravate the problem. Forget the printed instructions which are minimal, show a much different type of car and 2 different wire configurations, neither of which matches this product's wires.

The video is not too bad, but misleading. When it shows fishing the converter harness connectors through the fender to taillight location, it shows only the very start and then just as the second connector is pulled out into the tail light location. It skips all the time getting the fish line through, and then maneuvering two connector simultaneously through a tight fit around corners.

It is far easier to just cut the wires next to the connectors then pull only the wires through. Which is what I did after trying to get the connectors through the fenders and repeatedly getting stuck. Then reattached connectors to wires with crimp connectors. The install already requires you to have a crimping tool for the power wiring.

Getting a pull line though the fender route is tedious, but once that's done it's easy to pull the wires alone though.

Video does more or less the same thing with getting a fish line through the wire passage in the bottom of the trunk without getting stuck in the existing harness then routing the power wire. It shows the power wire emerging out into an open space below the car "where the drive shaft would be." That's fine unless you have a AWD Fusion, which has that drive shaft and rear differential and and differential controls and two rear drive axles all of which affect the wire feeding through floor and the wire route in that area.

Video also has on two mistakes in order of steps. It forgets to mention removing 2 push in retainers from trim across bottom of the trunk opening before popping the trim piece off. And video shows replacing that same trim piece before replacing the trim on side of the trunk. The side trim overlaps (underlaps?) the center bottom trim piece by about an inch. That is, side fits under center. The center trim is the last thing to go back.

Video shows attaching the power wire to the battery lug clamp nut which seems a marginal solution. Fortunately my car, unlike the car in video, has an unused vertical threaded stud on the lug which appears to be intended for attaching accessory power wires. I just had to provide a 6mm nut.


Excellent product. Easy install. Th anks


In the install video of the trailers lights for the ford fusion 2014 he uses a black hose to run the lights to the tail lights and to run the battery wire through the engine and you don’t include one and it took me two hours to do it with my own softer hose. If you included it women like me wouldn’t have so much trouble. thank you


A must for LED circuits. Works great.


It works well. I ran the power wire through the interior of the car and through the fire wall to keep it out of the weather. So the install took a while. About 3 hrs mainly figuring where to put the wire through the fire wall. I ended up going through a rubber grommet right behind the battery. Turned out perfect.

2013 Ford Fusion

Worked fine on my 2013 Fusion for towing a 500 lb trailer cries country.


Installation instructions made the job a breeze, wire lengths provided are more than sufficient.


Everything was good quality and works perfectly. Never having done it before, installation was quite a project. But by following directions and looking up how to dismantle the tail lights to do the wiring, I got through this project. I will tell you that the installation of the trailer hitch itself was much easier than doing the lighting wiring.

2015 Ford Fusion

Definitely not the easiest thing to install but that's not Curt's fault, although directions could have been more specific. Installed on 2015 Ford Fusion with limited issues. Biggest were feeding the tail light connections up through the trunk and feeding the power wire from the trunk to the battery. I did it under the backseat, along the trim and through a grommet in the drivers firewall (up behind the steering wheel), not the easiest but can be done. Watch some videos first and you will be fine. Oh and make sure you have all the right equipment and tools.

2014 Ford Fusion

Overall I am quite satisfied with this trailer wire adapter. (second one) My vehicle is a 2014 Ford Fusion. One improvement for this unit would be to install bullet connectors on the wires going up to the taillight adapters. As purchased they are very difficult to feed thru to the rear lights.


Great instructions and easy to install

2014 Ford Fusion

The installation video was a big help. Fishing the wires through those small holes behind the taillights was the most time consuming part of the whole project. Worked perfectly.

2014 Ford Fusion

Product was exactly as described. Shipping was super fast and the product was worth way more than paid for. Highly recommend.

Ford Fusion

Nothing against the product itself but the instructions itself was not very helpful as the variant of my Fusion was a PITA to fish the plugs out to the tail lights... Next time I shall cut and splice after fishing bare wires

2019 Ford Fusion

Great products and quick shipping

Wiring harness has worked perfect from the start. Ive been using it at least 20 times and without any problems. It was a small challenge to install but well worth the saving of doing it myself.
Joseph - 08/20/2020


It took me a while to pass the wires through. It took me about 2.5 hours. Saved some money doing it myself though. Good deal.

Show More Reviews

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

  • Does Curt Trailer Wiring Install Harness for 2017 Ford Fusion fit Hybrid Energi Models as Well
    Yes, the Curt trailer wiring harness part # C56351 that you referenced is a confirmed fit for your 2017 Ford Fusion Energi Hybrid model. These come with easy to follow install instructions that I have attached to this page for you to check out. I also attached a link to an install video for this kit that will walk you through the entire process as well.
    view full answer...
  • All Trailer Lights Come On While Using Curt T-Connector On a 2016 Ford Fusion
    In regards to the Curt T-Connector Vehicle Wiring Harness part # C56351 which is a fit for your 2016 Ford Fusion, I would first check to make sure you have the wire leads ran to the proper sides of the vehicle. The lead with green wire goes to the passenger side and the lead with the yellow wire goes to the driver side. If you have the leads on the correct sides then make sure the pin inside the connectors are all straight and non are corroded. I can't think of anything else that would...
    view full answer...
  • Installing and Troubleshooting Curt C56351 T-Connector on 2016 Ford Fusion
    Are you sure the extra wire you're speaking of isn't black? The Curt # C56351 will have two connectors that plug inline with the connection between the factory taillight harness and the taillight assembly. The one on the passenger side will have a green and white wire, the driver's side will have a white and a yellow wire. The converter box will also have two additional wires, one blunt cut black wire and one white wire with a ring terminal. The white wire grounds to the vehicle body, and...
    view full answer...
  • Tips For Installing Curt T-Connector C56351 In 2017 Ford Fusion
    I would be happy to give you a few tips to make getting the Curt T-Connector # C56351 installed in your 2017 Ford Fusion. First instead of pushing the pull wire up from the bottom, push it down from the top making sure enough of the pull wire is sticking out of the top so you have something to pull on. Having someone underneath guiding the pull wire down around the obstacles of the bumper will also making this a little easier. It can be kind of a pain, but stick with it and you will...
    view full answer...
  • 2018 Fusion Hybrid Curt Wiring Harness Installation Method
    I have attached a detailed video of our installer Rob going through all the installation steps of connecting the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector item # C56351 to a 2017 Ford Fusion. The Curt wiring harness is a confirmed fit for all model Fusions, including the hybrid. I recommend following the installation instructions and just doing what they say to do. The reason being is that the harness plugs directly into your Fusions rear tail lights on...
    view full answer...
  • Turning on Head Lights of 2016 Ford Fusion w/ Curt 4-Way Installed Gives Constant Power to Trailer
    While you mentioned the converter of the Curt T-Connector # C56351 being the issue on your 2016 Ford Fusion, that is pretty unlikely (possible, but not likely). For issues with the headlights, when turning them on causes constant power or a loss of function, the issue the vast majority of time is a bad ground somewhere. So check where you screwed in the ground wire on the frame, make sure it isn't loose or dirty or there isn't another connection issue and I'm very confident the issue...
    view full answer...
  • Comparing Curt C56351 & Tekonsha 118574 4-Pole Wiring Harnesses
    Curt 4-Pole Wiring Harness # C56351 offers a current output capacity of 5- and 7.5-amps per circuit, while the Tekonsha # 118574 has a lower maximum output of 2.1- and 4.2-amps per circuit. This is the only practical difference between them. Both install in the exact same manner, as illustrated in the linked video and article. If you are unsure of the power draw from your trailer go for the higher-rated Curt harness to avoid any potential for overload.
    view full answer...
  • Trailer Wiring Recommendation for a 2015 Ford Fusion Titanium
    The Curt Wiring Harness part # C56351 that you referenced has been confirmed as a fit for your 2015 Ford Fusion Titanium. The part number # 42475 that you also referenced is for Jeep vehicles and would not work.
    view full answer...
  • Right Stop/Turn Pin on 4-Way for Ford Fusion Active All the Time
    I am sorry to hear about the issues you are having with your wiring harness. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part # C56351 is correct for a 2013 Ford Fusion SE. If the right stop/turn signal pin on the 4-way has constant power without either signal active then there is an issue with the converter box and the unit will need to be replaced. For replacement, I recommend the T-One Vehicle Wiring Harness part # 118574. The reason for this is that...
    view full answer...
  • Troubleshooting Lights After Installing 4-Way on 2014 Ford Fusion
    It is likely the result of a bad ground, but in order to determine the specific problem you'll need to use a circuit tester such as # 40376 to test the connector on your Fusion after disconnecting it from your trailer. Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring. If the signals going to your harness are okay, you'll need to test the signals coming out of the harness,...
    view full answer...
  • Comparing Curt and Tekonsha Brand Trailer Wiring Harnesses for 2016 Ford Fusion S
    Actually I have a third option for trailer wiring that I would recommend for your 2016 Ford Fusion S. The T-One kit part # 118574 is the best option as it has higher amperage ratings which means it would be harder to short out and permanently damage. I attached an install video for you to check out as well. As far as Curt goes the part # C56351 is the newer design than the # C56302 that you also referenced which has their older style converter box.
    view full answer...
  • Does the Curt T-Connector Vehicle Wiring Harness Work With 2017 Ford Fusion Sport
    The # C56351 Curt T-Connector Vehicle Wiring harness is a confirmed fit for all models of the 2017 Ford Fusion. This means it will work with your 2017 Ford Fusion Sport. However, I recommend the # 118574 Tekonsha T-One Vehicle Wiring Harness. This is also a confirmed fit for your Fusion Sport. The reason I recommend this wiring harness over the other is because we have found it to be the most reliable. I have attached an installation video on a 2017 Ford Fusion for your reference.
    view full answer...
  • All Trailer Lights Come On With Headlights Turned On In a 2013 Ford Fusion
    I spoke with Curt and they informed me that you may have the incorrect trailer wiring harness. In order to confirm this I will need you to check the 10th digit of your VIN. If the 10th digit is a "D" then the Curt T-Connector Vehicle Wiring Harness part # C56351 is correct but if the 10th digit is a "C" then the Curt T-Connector Vehicle Wiring Harness part # C56048 is correct. The 10th digit represents the year the vehicle was manufactured. In the past, we have had issues with vehicle being...
    view full answer...
  • Troubleshooting Incorrect Trailer Lighting with Curt C-Connector on 2013 Ford Fusion
    It very well could be that the converter box is bad on your Curt T-Connector # C56351 but before going that route I recommend you do some testing first. Try testing each of the functions individually by using a circuit tester like part # PTW2992. I have attached a photo showing what function each pin should carry. If you are still getting the same problem then try testing each of the wires before it goes into the converter. The green will be right turn/stop, yellow will be left turn/stop....
    view full answer...
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  • Trailer Wiring Recommendation for a 2016 Ford Fusion Titanium
    The Tow Ready Wiring Harness part # C56302 is trailer wiring that has been confirmed as a fit for your 2016 Ford Fusion Titanium so I would recommend it for you. If you need a trailer hitch the Curt part # C56351 has been confirmed as a fit. For a 1-7/8 inch ball mount the part # C45561 would work or the # C45562 for a 2 inch ball.
    view full answer...
  • Troubleshooting Curt Wiring Harness with Running Lights Not Functioning on 2013 Ford Fusion
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56351 is the correct fit for both 2013 and 2014 Ford Fusion models. The harness does not "sense" power using sensors but rather is a direct plug into that wiring circuit. Since you are getting no running lights, I recommend disconnecting the left and right side to check for bent pins and then make sure the ground is connected bare metal to bare metal. Using a little dielectric grease # 11755 may also help...
    view full answer...
  • Recommended Trailer Hitch Receiver to Fit 2016 Ford Fusion Titanium
    The Curt Class II Trailer Hitch Receiver with the Euro Draw Bar # C120911 is confirmed to fit your 2016 Ford Fusion Titanium. Or if you prefer the 2 inch hitch ball # C120912 will also fit your Fusion. Since you're planning to use the hitch for a cargo carrier, the Curt Class II Trailer Hitch # C12091 is the same hitch receiver with no ball mount. Then for a cargo carrier you can use the Curt Cargo Carrier # C18110 which will fit the Class II hitch and measures 20 by 48 inches. If you...
    view full answer...
  • Can a 2016 Ford Fusion be Used to Carry a 200 Lb Scooter
    I do have an option for you but your 2016 Ford Fusion only has a 200 tongue weight capacity. The Curt Trailer Hitch Receiver part # C12091 that you referenced which is a fit for your Fusion has a 350 lb tongue weight capacity but since the vehicle is lower it will need to be the figure you abide by. The weakest component when you are towing or hauling is always going to be your limiting factor. The other issue you would run into trying to haul a scooter with the above trailer hitch is...
    view full answer...

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Info for this part was:

Employee Mike L
Expert Research:
Mike L
Employee Jameson C
Expert Research:
Jameson C
Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Video by:
Kathleen M
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B
Employee Amanda M
Written by:
Amanda M
Employee Robert C
Test Fit:
Robert C

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