1. Custom Fit Vehicle Wiring
  2. Curt
  3. Custom Fit
  4. Trailer Hitch Wiring
  5. 4 Flat
  6. Powered Converter
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 # C56251
lowest price pledge
Our Price: $67.22
You Save: 46%
Custom Fit Vehicle Wiring

Will this fit?

To see if this custom-fit item will work for you please tell us what vehicle you'll use it with.

Orders above $99 qualify for Free Shipping
Shipping Weight: 1.91 lbs
In Stock
Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Custom Fit C56251
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Need help with installation?
Locate installers near me
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. Call 800-298-1624 to order Curt custom fit vehicle wiring part number C56251 or order online at etrailer.com. 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.
  • All Info
  • Reviews (20)
  • Q & A (4)
  • Videos (3)
  • Photos
  • Why etrailer?

Curt Custom Fit Vehicle Wiring - C56251

  • 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 - no cutting or splicing of wires
    • Locate connection points on the driver's-side, behind the tail light and beneath the vehicle
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes a tail light converter 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 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: 3 amps per circuit
    • Tail lights: 6 amps per circuit
  • Limited 1-year warranty


This custom-fit T-connector plugs into your vehicle's wiring harness, which is located on the driver's-side behind the tail light and beneath the vehicle. You will have to remove all cargo area floor coverings, storage trays, and the scuff panel to access these connection points. 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.

56251 Curt T-Connector - Surface Mount Technology - 4 Wire

Installation Details C56251 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Video of Curt T-Connector 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 Curt T-Connector Vehicle Wiring Harness Installation - 2011 Kia Sportage

Clayton: Hello, everybody. Clayton here at etrailer.com. At etrailer.com we test fit, install, and review a ton of different products to help you as a customer make a more educated decision for your vehicle.And today I have a 2011 Kia Sportage. We'll be taking a look at, and I'll show you how to install, the CURT T-Connector 4-Pole Wiring Harness. Our 4-Pole wiring is going to allow us to get those necessary lighting functions back to our trailer or cargo carrier. This is going to allow us to not only travel legally, but also safely.

Our 4-Pole is going to have a nice dust cover to protect our plugs from the elements.Now, this is a pretty easy kit to get installed. One really nice feature about it is that it's plug-and-play, so we don't have to splice into any of our vehicle's wiring. Also, our module is going to be contained inside of the vehicle behind the grommet, so we don't have to worry about any dirt or debris getting in that module and potentially screwing up our wiring going down the road in a few years.Now, in terms of installation, this really isn't that bad to get installed. Like I said, it's plug-and-play. The hardest part is going to be running our wire up to our battery.

So we've gone over some of the features. We've talked a little bit about installation. I'll show you how to get this installed on your car now.To start our installation, we're going to be removing a wiring harness located here behind our driver's side wheel. As you can see, there's a plug right here. Just want to pull out here and try to get this clip undone.

If we actually pinch it together, we can push it out. Now we just want to push down on this tab and pull our plug apart. So again, we're just going to push on this tab and then pull our harness apart.Now we're going to grab a nylon pry tool and pull this grommet out of our floorboard, just like that. Then we just want to cut this grommet. We do want to be careful not to cut the wiring inside of the grommet.

Once we get through the grommet completely, we can remove it and it'll be re-installed in a later step. With our grommet removed, we just want to push our plug back up into the car. Now we'll move up to the top side.Now the trunk area of our vehicle, we went ahead and lifted out the trunk liner. We now need to remove three of these plastic push-pins on our back panels. We're going to grab a small flat-blade screwdriver, carefully unthread it. You don't want to push too hard or else it won't come out.Now with that released, we can grab our trim panel tool. Pry out on the head of the plastic push-pin. Pull the push-pin out on the bottom and kind of pry the whole thing out. We'll repeat that same process for our other two push-pins.With our three fasteners removed, we can now pull up on our kick panel. You want to work your way from left to right. We now lift our kick panel out and set it off to the side. We're now going to be removing three Phillips-head screws; one located here, one located here, and one located here. That's going to allow us to pull this panel out a little bit and work behind it. Again, there's three Phillips-head screws.We can now remove our left tail lamp. We're going to grab a Phillips-head screwdriver and remove this screw and this screw. With our two screws removed, we can pull back on our tail lamp. We just want to pull straight back, towards the back of the vehicle. Just like that, we have our taillight assembly out. We're now going to push down on this tab here and then pull straight back to disconnect our tail lamp. We can set this off to the side.We can now I grab a nylon pry tool. We're just simply going to pry out on this body panel here. It's kind of hard to see down here, but if we reach down you can grab that harness that we pulled up through the bottom. We can now grab our new wiring harness. We are now going to take this side here and simply slide it over our plug. You hear a nice, audible click. Now we can grab our module and drop that back to through bottom.In our case, we do have a bracket on our hitch to mount our 4-Pole wiring, so we're just going to drop everything back through. Before we can drop our wiring through the bottom, I do want to strip this back just a little bit more and then we can add our black wire for the power. Again, we're going to be using the black wire off of our module.I'm going to grab our provided butt-connector. We'll crimp that down, then grab the long black wire provided in our kit. We'll strip that back. I'm going to trim a little bit of that off. I left too much. And then we'll simply add this to the other end of our butt connector. I'm going to come back and add some electrical tape to this, just to be safe.We're now ready to drop everything but our module and our ground wire through that hole in the bottom of our car.We're now ready to mount our module down here with our two-sided tape. We're going to peel back one side of this tape and stick it to the backside of our module, just like so. We're mounting our module right here on the underside of our rear facia. You want to make sure to hold it down for a few seconds, just to make sure that that two-sided tape is going to stick.We're now ready to mount our ground wire. I'm just going to run it right down here next to our grommet. We can use our supplied self-tapper. Before we go any farther. I want to take that grommet and just add it to our wiring right here. That way we know it's protected in our vehicle. With our grommet re-installed. We can now push our body panel back into place and then reinstall our screws.We can now take our plug that dropped through that grommet and plug it in right here where we disconnected that plug earlier. We'll plug that in and then push this plastic connector back into that hole in our frame. Just like that. Now we can zip-tie up some of our wiring and then we'll go back on top of the car, drop a pull wire down and pull up our taillight connections.We're now ready to run our black wire up to our battery. Now it is important to stay away from anything moving, so that's going to be suspension components or your driveshaft if your vehicle is all-wheel drive. And we want to stay away from anything hot, so that's going to be our exhaust. I'll go ahead and show you how I routed ours.This is where our wiring comes out, I ran it right up here along our brake lines. Followed this brake line up over our sub-frame. Pulled it out right here. Luckily there was enough factory lines to follow, so we just followed those factory lines up behind our fuel tank, then under this underbody panel. It comes out the underbody panel here. I just zip-tied it to our factory lines here. Ran it all the way up to here.We're now going to drop our air line tube through this gap where our taillight was. You can also use a coat hanger or a string with a nut on the end. Basically, just anything that can get down to the bottom to help us pull our wiring up.With our air line tube pulled through the bottom, we can now grab our plugs for our taillight assembly. We're just going to grab some electrical tape, tape our plugs onto our pull wire, and we can pull them up through our facia.Moving up top with our wires pulled through, we can remove our electrical tape. Want to grab the gray plug. Just want to line it up with our factory plug for our taillight and plug it in there. You hear a nice click. Give it a little pull, make sure it's not going anywhere. Grab the new end of our plug, slide it into our taillight. You heard that nice click. Give it a little pull to make sure we're not going anywhere. Carefully put our wiring down here and then re-install our tail lamp in the reverse order that we took it apart.And I want to take that same pull wire, try to follow a good path going through our engine compartment down to the ground. Again, stay away from anything hot or moving. So, I'll just get this pull wire dropped down and we'll pull our power wire up and make our battery connection.I'm going to try to follow these factory lines right down the backside of our battery. Now you're going to tape our air line tube to our power wire. We can go back up top. We can now pull our power wire up. And I'm just going to zip-tie it to a couple of lines back here, just to secure it. That way it's not going to move after we make our connection. We'll cut it off and grab our wire strippers. Strip back one end just like so. And grab our butt connector provided. Add that to our wire. I'll just crimp it down.Now we can grab our fuse holder provided. It comes pre-stripped. All I have to do is pull back the covering and twist that and add it into our butt connector, and we'll crimp it down. On the other end of our fuse holder, we'll pull off that rubber cap, grab our provided ring-terminal, add that to our wire, and we'll crimp it down. And, again, I'm going to add some electrical tape just to ensure a good connection.We are going to be connecting this to the positive side of our battery, so we're going to lift this cover off. We're going to be using this bolt here, so use a 10 millimeter socket. With this removed, we can grab our ring terminal, slide it on like so, and then re-install our 10 millimeter bolt.When we go to close our lid, it isn't going to close all the way, so we just want to trim out a little square here using our snips. That way it fits over our new wire. With our notch cut out, we can slide our cover back over our wire, snap it into place. And we can grab our ten-amp fuse provided. All we want to do is push that into our fuse holder just like so. We can close our cap.Now, let's hook it up and test everything out. If you don't have a tester, you can find one here at etrailer.com. We'll go ahead and test it out. We'll start with our brake light signal. Now we'll try our running light signal. And do our right turn and our left turn.At this point, feel free to re-install everything in your trunk.Went ahead and cleaned up our wiring. Our hitch did have a bracket for a short mount for our 4-Pole, so I went ahead and threw that on there. You can find one of those here at etrailer.com, if you do have that option on your hitch.With all that being said, that's going to complete our look at and the installation of the CURT T1 4-Pole Wiring Harness on our 2011 Kia Sportage.

Customer Reviews

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - C56251

Average Customer Rating:  4.8 out of 5 stars   (20 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.

- C56251

Installed the lighting kit when I installed the trailer hitch. The wiring harness worked perfectly and made pulling the trailer a breeze.

- C56251

The wiring system worked exactly as described and the video guide was very helpful. Other than a few rusted bolts on my vehicle I installed the system with no issue and so far it has function and worked well within my expectations for a full year. Great product.

- C56251
2014 Kia Sportage

This wire kit was pretty easy to install; the directions were very detailed and accurate. The only issue I ran into was there is a point in the instructions where you're running wires through a grommet that is way too small for the connectors and the instructions reference a new grommet that is not part of the kit. I just cut the old one to fit the new wires th through the side and it was all good. Routing the 12v wire was pretty simple; I had my car backed up on a pair of ramps and ran the wire along the brake and fuel rail on the driver side under the car. I punched this one up through that grommet too to plug in at the module. I don't use butt connectors; I always solder and heat shrink. Personal preference. In all, this was a straight forward and simple install.

The hitch and wiring are still going strong! Ive had no issues at all.
Flash - 11/01/2017

- C56251
2016 Kia Sportage

Wiring product was good but missing the grommet for the 2016 Sportage. Other then that pretty self explanatory

Love your products. It is the only hitch I will purchase and your wiring kit was fantastic. I work at different campgrounds around the country, mainly east coast but I tell everyone about your products. Thanks for making products that actually fit and do what what consumers pay for. Love your stuff.
Kevin S - 02/20/2018

- C56251
2011 Kia Sportage

The process of installing the Curt T-Connector Wiring Harness for my 2011 Kia Sportage went very well. I knew it would take quite a bit of time because of all the removal of the tail light, inner panels, etc. However, it is worth the time because of end result - a system that works, and appears almost factory installed. I highly recommend this product.

- C56251
2012 Kia Sportage

I love buying stuff from Etrailer.com. The listed products are the exact fit for my vehicle. The on line instructions make it very easy to install. I installed the hitch and wiring harness in just under 2 hours. I will buy stuff from this site again

- C56251
2014 Kia Sportage

Arrived as scheduled. Package contained all necessary parts and in good condition. Very pleased with the product . Harness was easily installed and works great. Glad I found this company

- C56251

Fit perfectly and as expected. Installation was a little challenging but the walk-through was very concise. Thank you. I will definitely order from etrailer again in the future.

- C56251

Would have loved to have had a grommet made into wires on t connector that goes through trunk pan, down to factory harness that goes to left rear tail light. Would gladly have spent a few more dollars for that bit to be pre made than having to cut the grommet and then patch it with the rtv sealant. Besides that, install went very well.

- C56251
2016 Kia Sportage

Arrived sooner than expected. Haven't installed yet but looking over instructions appears they appear clear and easy to follow for me not having much knowledge on wiring anything. Great follow up with notification from etrailer. Install will hopefully be tomorrow.

- C56251

Easy to install. Instructions need to be slightly modified for the 2016 model year. Missing replacement rubber grommet that was supposed to be included in the kit, otherwise okay.

- C56251
2015 Kia Sportage

looks like everything is there but box was damaged and hitch was sticking out

- C56251

All your product are well explained. I love the videos. Help out HUGE! It helps because so many makes and models. Give you a little idea of what you will encounter on the install.

- C56251
2011 Kia Sportage

Easy to install and works great so far.

- C56251

Wonderfull web based support. Great attention and very polite attentive service

- C56251

Wiring was easy for a DIY and worked Totally as Advertised.

- C56251

- C56251
2016 Kia Sportage

Everything came in one box. Great site to grab everything in one spot. Will order again.

- C56251

- C56251
2013 Kia Sportage


Ask the Experts about this Curt Custom Fit Vehicle Wiring

  • Troubleshooting Turn Signals After Installation of Curt 4-Pole Wiring Harness C56251 in Kia Sportage
    Thank you for your wiring harness purchase. The Curt 4-pole wiring harness kit # C56251 is a custom-fit product confirmed to fit your 2012 Kia Sportage. Since this installs using connectors that match those on the car there really is no wiring diagram per se, but the instructions are linked for you. Only the one power wire to the battery requires a spliced connection; this goes to the positive terminal via the included fuse holder. You do not mention whether it is the vehicle or trailer...
    view full answer...
  • Troubleshooting Parking Lights Not Working With Curt Wiring Harness Installed On 2013 Kia Sportage
    I am sorry to hear you are having an issue with the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56251 installed on your 2013 Kia Sportage. Since only one function was not working with the harness installed, I recommend double checking that all of the pins in the connector that plug into to the factory driver side connector are not bent causing a the connection to not be complete. Also make sure that the connector clicks in to the factory connector. If...
    view full answer...
  • Curt Trailer Hitch and Wiring Harness Fits for 2016 Kia Sportage
    The correct Curt 2-inch Class III hitch for the 2016 Kia Sportage is part # C13120. This also fits the 2015 model year. This Curt hitch comes complete with all required installation hardware. I have linked the written instructions as well as an install video showing a 2015 model year. The only specialized tool needed is a torque wrench like # ALL944001 which will let you tighten the fasteners to the correct torque values. If you plan to move the hitch from one vehicle to another please...
    view full answer...
  • Lighted Hitch Cover Remains On with Vehicle Lights Off
    A lighted hitch cover such as # CR-017 uses the same type of 4-pole wiring as a trailer that has basic lighting functions. This type of wiring set-up provides brake, turn and tail light functions. This 4-pole wiring harness, such as # 118526 and # C56251, will pass a very small amount of power even without any vehicle lighting functions activated. If you have a hitch cover that uses highly efficient LEDs instead of bulbs, like # CR-017, it may illuminate just from the small amount of...
    view full answer...

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

  • Why etrailer.com?

    At etrailer.com we guarantee:
  • Highest quality custom fit vehicle wiring for the best price.

    Our Lowest Price Pledge ensures you will never overpay for the parts you need.
  • Real product know-how.

    We make sure that the products we sell are what we say they are, and that they work the way they are supposed to work. Get real advice from a real person who has the knowledge and expertise needed to solve your problem.
  • Most detailed, accurate custom fit vehicle wiring information available.

    Because we take providing accurate product information seriously, we take our own detailed product photos, demo videos and installation videos, as well as verify measurements, instructions, and vehicle fit information.
  • Installations, made easy.

    We love helping people and have the most highly-trained customer service, hands-on experience, step by step videos and installation instructions.
  • Fast shipping.

    Your order is automatically routed to get out of our warehouse and to your door as quickly as possible. Receive free shipping on orders over $99.
  • Personalized service for life.

    We provide one-on-one, personalized service from the ordering process through the life of your product.
  • Trusted since 1946.

    We've been serving customers since our parts store first opened in 1946 and continue to be recognized by our customers, our vendors and third parties for exceptional service.
  • Returns Policy

    Need to return an item? No problem. Please read our Returns Policy for more information.

Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jacob T
Video Edited:
Jacob T
Employee Chris R
Video Edited:
Chris R
Employee Adam R
Expert Research:
Adam R
Employee Cole B
Installed by:
Cole B
Employee Chelsea B
Written by:
Chelsea B
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B
Employee David F
Test Fit:
David F
Employee Clayton O
Test Fit:
Clayton O

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.