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  1. Custom Fit Vehicle Wiring
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  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 # C56381
Our Price: $58.55
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Custom Fit Vehicle Wiring

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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. 1-800-940-8924 to order CURT custom fit vehicle wiring part number C56381 or order online at Free expert support on all CURT products. Great prices 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 (6)
  • Q & A (0)
  • Videos (1)
  • Photos
  • Why etrailer?

CURT Custom Fit Vehicle Wiring - C56381

  • 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 in rear cargo area
    • 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: 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 in your rear cargo area. You will have to remove the trunk floor coverings, storage trays, rear scuff panel, and side trim panels 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.

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.

56381 CURT T-Connector Vehicle Wiring Harness with 4 Pole Trailer Connector

Installation Details C56381 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 Custom Fit Vehicle Wiring - Trailer Hitch Wiring - C56381 Review

Today we're going to take a look at the Curt T-Connector Vehicle Wiring Harness with the four-way flat trailer connector. This is a custom fit part. It's designed to fit the 2017 Hyundai Ioniq Hybrid. On a custom fit part, I always like to recommend for you to go to our website, use our fit guide, put in your year and model vehicle, and it'll show if this will work for your application. This harness will provide this four-way flat trailer connector to the back of your vehicle to power your trailer's signal lights. This is compatible with five-pull, six-pull, and seven-pull adapters that we sell on our website. This harness does connect very quickly and easily.

Basically, you just locate your connection points in the rear cargo area, plug in these t-connectors - one on each side. One on the driver's side and one on the passenger's side. Ground your white wire and then run your power wire to your vehicle's battery. This harness does include this tail light converter, this black box here. This is to ensure that your vehicle's wiring will match that of your trailer.

It's a power module so it connects directly to the battery to avoid overloading your vehicle's electrical system. This is constructed using SMT technology, which is surface mount technology. This will give you a more consistent and reliable performance. It helps maximize your trailer light yield and intensity while producing minimal heat and it will ensure superior operation in any rough road conditions. This also comes with this nice dust cover for the four-way so what's nice with that is when you have this installed on your vehicle, you can install the dust cover and you just put it on and then when you're not plugged into a trailer, it'll protect those terminals from any damage from the elements. These parts are made in the U.S.A. A few specs on this - the maximum amp reach on the stop and turn light circuits is 3 amps per circuit.

On the taillight circuit, it's 6 amps total. Now it does come with a nice set of detailed instructions and it'll describe how to install everything and even give you good pictures on where your connections are made. Simply, when you go to install this, what you want to do is go to the rear of the vehicle, the rear cargo area, and then you want to locate your connection points, which are on both sides. On the driver's side you want to start. Take this t-connector with the yellow wire in it. That's for the driver's side and then you unplug the connectors in your vehicle.

Plug these in there. You have the white wire with the eyelet on it. That you want to connect to good clean ground if there's one nearby. If not, they give you a screw that you can make your own ground. Then you'll take your other t-connector and you have this length of green wire here. This is for the passenger side. Run this all the way over to the passenger side. Same way. Plug this into the connectors on that side. Now your converter here, this black box, you do want to attach that to a nice flat service so it doesn't bounce around. They do include this piece of double-face tape that you can use to attach it down and then run your bonded wire for your four-way all the way out the back. Then your last wire is this black power wire. This needs to run up front to the vehicle's battery so they do include this length of wire to do that and the connectors. You take one of your butt connectors, put it on the power wire, connect it to the one end of the wire, run this all the way up to the front. When you get to the front, you don't want to connect this directly to the battery. You want to run it through that end-line fuse holder. Take your other butt connector and connect it to one side of the fuse holder just like that. Then your other side of the fuse holder, you want to take this eyelet connector and install it and then connect this to the battery at the front of the vehicle. Once that's all connected, pop it open. Take your included 10 amp fuse. Install it into the fuse holder. Put your cap on there and then your system will be all ready to go. Now they do include some extra cable ties to take up any slack in the wiring. If any wiring is hanging down, you can zip it up with the cable ties and your system will be all ready to go. That should do it for the review on the Curt T-Connector Vehicle Wiring Harness with the Four-way Flat Trailer Connector.

Customer Satisfaction Score:

Customer Reviews

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - C56381

Average Customer Rating:  5.0 out of 5 stars   (6 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.


Excellent instructions. When I discovered the wire would need to run from the back all the way to the front for the power source it felt it was going to be a real challenge. Following the instructions and the added videos from etrailers it was easy and no self modifications were needed. Everything was the same on my car as in the photos and videos. Great job etrailer for publishing new videos when changes are made to different year models of car’s.


Kit included everything I needed, and clear instructions. Works perfectly


Fits just right. Went on my 2018 Ioniq without issues. Seems well made.


Good product quickly delivered. Great customer service and follow-up.

2020 Hyundai Ioniq



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

  • Power Wire Routing From Battery to Vehicle Trailer Wiring Harness
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56381 requires power directly from the battery. You will need to run that power wire away from hot or moving parts up to your vehicle battery. To do so, there are 3 common methods. I've attached an article to assist with the routing of that power wire with information to help with each one for you to determine the best fit for your vehicle.
    view full answer...
  • 2017 Hyundai Ionic Sealed Battery Trailer Wiring 12V Power Connection
    I reached out to my contact at Curt and for your 2017 Hyundai Ioniq using wiring harness # C56381, you will connect that 12V power wire for the harness to the lithium ion starter battery under the back seat on driver's side. It is a little difficult to discern because it is part of the same housing as the larger battery, but this is a separate charging battery specifically for the starter but this is where you will connect your harness.
    view full answer...
  • Turn Signals Don't Work on Trailer With C56381
    There are a number of troubleshooting steps you can take if your trailer's turn signals don't work after you installed the Wiring Harness # C56381 on your Hyundai. The first thing to do is take a look at your owner's manual to locate any trailer fuses or relays and ensure they are all there and in working order. If they are, in order to determine the specific problem you will need a Circuit Tester like # PTW2979 and test the connector on your vehicle after disconnecting it from your trailer....
    view full answer...

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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Jameson C
Expert Research:
Jameson C
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

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