bing tracking image
  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

lowest price pledge
Our Price: $32.41
You Save: 35%
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: 0.86 lbs
In Stock
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

Customer Photos

Need help with installation?
Locate installers near me
Quickly and easily install a 4-way trailer connector on your vehicle with this custom harness. 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 C56040 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.
  • All Info
  • Reviews (1693)
  • Q & A (0)
  • Photos
  • Why etrailer?

CURT Custom Fit Vehicle Wiring

  • 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. 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 point in rear cargo area
    • Plug in connector
  • 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 behind the interior trim panel in your rear cargo area. Once you've plugged in the converter, insert the included 10-amp fuse into the integrated fuse holder.

Once installation is complete, the 4-way connector will be stowed in an out-of-the-way location within your cargo area. Adhere the black converter box to the frame of the car using the double-sided tape provided. Secure any loose parts of the T-connector with the provided cable ties.

It is recommended that you use a small amount of grease on all electrical connections - the plug 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.

2010 Subaru with Backup Sensors

56040 CURT T-Connector - Surface Mount Technology - 4 Wire

Item # C56040

Installation Details C56040 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 - C56040

Average Customer Rating:  4.9 out of 5 stars   (1693 Customer Reviews)

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

2015 Subaru Forester

This is the second trailer hitch and wire harness I've bought from etrailer and I am beyond satisfied! They leave no stone unturned for instructions and customer service. The video tutorials and the products are fantastic. I will never go anywhere else for trailer hitch and accessories.


This went on without a problem on a 2022 Subaru Outback thankfully providing the built-in wiring harness that is located under the right side rear trim piece, I did not need to remove. I used 3M Dual Lock in case the control unit needs to be easily moved in the future. Using this for a OneUp Bike Rack and their license plate and LED light bar.


Easier to run the cable through out the spare tire and attach the connector to the hitch outside.

2019 Subaru Forester

Easy to install, even the videos that came with it was super to follow and when I was installing my tow hitch I figure it out where I can run the cable instead of just having it run from the trunk, I’m just worried that it’s gonna brake from time but I figure to wired it elsewhere

Thank you for your feedback. I wanted to assure you that the weather stripping will protect the harness wires. The wiring is free to move in and out with little resistance that will work long term for you.
-- Etrailer Expert Jenny N - 11/01/2021


Only lasted about six months. One day taillight circuit just stayed powered on all the time regardless of light switch or key switch position. There was no fault with the vehicle, module on trailer harness went bad. Replaced harness and now works again per design.

It sounds like your harness was shorted out or there was corrosion on your connector. I am glad its working out now!
-- Etrailer Expert Sierra K - 06/20/2022

2020 Subaru Outback Wagon

Easy installation. For the 2020 Outback, instructions were wrong about location of connection. Subaru moved the harness connection to the passenger's side, against the rear of the space for the spare tire. See Image.

Works great.
John F - 07/25/2021


The box was crushed and the hitch was sticking out of the side. It was all scratched on the end
The connector was not sent or fell out of the package.
I called customer service
They told me that they would be delivering a new one for me.

Can you make sure that the connector was shipped to me today?

Just a suggestion.....maybe you should tape the connectors to the hitches before you box them

I will have our Customer Service team reach out to you.
-- Etrailer Expert Jenny N - 04/21/2022

2021 Subaru Outback Wagon

Super quick and easy installation. Since I seldom use the trailer, I left the wiring harness inside.

This works perfectly, since I only use my trail once in a while, I just bring the wire out under the tailgate
Steven R - 05/04/2022


I'm at the year mark of owning an etrailer 2" receiver. I have nothing but praise for this item. The install went incredibly smooth. It was ready way sooner than expected.

I've only used this to haul several bicycles, but it's very sturdy and easy to use between the bike rack and/or a hitch.

It's installed on a Subaru Outback and well worth it if you're on the fence between other products.

Year later: The receiver is still holding strong. No issues even with our MO weather. 5 out of 5, would still recommend
Ryan - 02/21/2022


The wiring harness for my trailer by Curt was essentially “plug and play”. The harness was extremely easy to connect and install. The hardest detail was figuring out where Subaru hid their end of the harness so I had something to plug into. Fortunately Subaru had also made their car user friendly, so different panels that provided access simply snapped in and out. Without reservation I recommend the Curt harness for complete directions, quality of manufacture and overall attention to detail

2017 Subaru Outback Wagon

5 stars for the wiring harness which works just fine in my 2017 Subaru Outback Wagon. The install took some time though (more than it took to install a Curt hitch) because it was hard to locate and expose the car's wiring connector. Would give the install a 3 star for that. The harness instructions have pictures showing where to find that connector behind a panel covering the left rear wheel well. But you don't know exactly where behind that panel, and it's a tight squeeze getting your hand & forearm in there to find it. A small mirror helped. The harness is looped back on itself so you won't see the connector, look for the loop and maybe some blue tape which holds the loop. It's finding that loop that took the time.
I routed the harness out through a rubber plug in the spare tire well. It's easy & much neater than running it under the tailgate when you're towing. Remove the rubber plug, slice it from the center to one edge so you can get the wiring harness into it. Figure out how long a wire you need outside the car, reinstall the plug, and seal around the wire with 100% silicone caulk.
I connected the grounding wire to an existing bolt inside the car (just secure with a second nut) rather than drilling a new screw hole.

No issues at all, works as it should.
Charles - 03/17/2019

2021 Subaru Crosstrek

Hitch is well built and installed fairly easily by just myself. Another set of hands would be nice when lifting the hitch in place but it's certainly doable. Looks great! Installation videos are a great help.

Subaru Outback Wagon

When I bought my used Subaru Outback, it came with an installed trailer hitch, but not a light wiring harness. Installing this harness was easy and went fairly quickly. It tucks away in the spare tire wheel well, and it's easy to access and drape underneath the hatch door when in use.


This review is about the installation process, which did not go without a hitch. one of the 4 nuts that are used for mounting was too large. I had to interrupt installation so I could buy a 7/16-14 nut. Otherwise, installation was easy.


A great hitch in wiring harness! Installation was easy! This is my second hitch from e-trailer. Highly recommended!

Awesome product, easy install, reliable!
Don - 02/07/2022


Awesome kit! Installed in no time and running my trailer lights perfectly. Great fit for my application.

Still going strong. Controlling my trailer lights very well. I remember installing still and it was a great fit for the application. Easy to touch away even not in use and just a solid wire and plug solution.
Wesley - 04/24/2022

2022 Subaru Outback Wagon

Very easy install. Be careful with the 4 plastic connectors under rear trim plate, broke one without much pressure at all. Also, the double sided tape had no stick to it, so you might need to buy some good double sided tape to mount the module in spare tire area.


Easy to install as detailed in the instruction video. I have purchased several hitches and wiring harnesses from e-trailer and have never had a problem.


It seems way late in the day for Curt to be putting out erroneous instructions, as the location of the wiring connector has changed in the 2020 Outback; that "tech tip" of yours ought to appear on the main page for the wiring harness. I am disappointed to have to deal with this. The new video turns out to be a must.

I agree that it is quite annoying that the regular instructions are not more clear that the 2020+ vehicles have changed locations of the factory connector from the rear drivers side, to the passengers side. They are probably waiting to check for future years of this vehicle to become available to test and update instructions. This is why etrailer makes installation videos to help out our neighbors with tricky instructions. I have attached the video which shows the location swap at the 4:20 mark.
-- Etrailer Expert Sierra K - 12/22/2021

Subaru Forester

Great product, easy install. Installed on a 2021 Subaru Forester in my yard. Took under an hour including wire harness. As always excellent instructions. I'm a lifetime customer. This is my fourth hitch and just get better.

2021 Subaru Forester

The placement of the connector in the back of the Subaru Forester allowed me to plug in the wiring harness and let the excess cable, box, and fuse sit in the back tray of the forester. I grounded the harness to a nearby bolt and bracket. I feed the wire out of the back of the hatch when needed.


The Subaru vehicle harness has a built-in receptacle, so after locating that and attaching ground wire, this really is a plug and play!

Initially, I wrapped a single layer of duct tape around the wires at the point where they pass through the hatch to protect against any possible rubbing. Since then I purchased an 18 extension which transitions the hatch.
Allen - 02/26/2022


Great product, terrible installation instructions. Thankfully, [online] is filled with much better walkthroughs. Paper instructions had sparse info and unreadable pictures.

I recommend watching the video that we have on a 2016 Subaru Outback Wagon.
-- Etrailer Expert Jenny N - 05/05/2022

2017 Subaru XV Crosstrek

Installing this powered trailer lighting adapter was pretty easy, the most difficult part being removal of the trim panels. If you haven't done this sort of thing before you'll find that an inexpensive set of trim removal tools will be a significant help. Subaru did the wiring job properly - contrary to what I expected you don't have to run a hot wire to the battery, a hot is already present at the connector - and the actual hookup is pretty easy. The assembler who secured the connector pigtail at the factory was perhaps overly enthusiastic with the electrical tape so a sharp knife and some careful dissection was required to avoid damaging any wires.

While the instructions suggest drilling a hole and using the included self-tapping screw for the ground wire, on my 2017 Crosstrek that wasn't necessary as Subaru has thoughtfully provided a tapped hole for an M6 screw in the perfect location. I used an M6-100 hex head bolt with both a flat washer and a lock washer.

2020 Subaru Outback Wagon

Easy install, especially considering the video instructions. Took about 40 minutes tops and tested out fine. Very happy with this harness.

No issues though I have used very sparingly. But all is well so far.
Michael M - 02/08/2022
Show More Reviews

Ask the Experts about this CURT Custom Fit Vehicle Wiring

< Previous
123. . .11

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

  • Why

    At 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 Joe V
Test Fit:
Joe V
Employee Nicholas E
Test Fit:
Nicholas E
Employee Shane T
Test Fit:
Shane T
Employee Randy B
Test Fit:
Randy B
Employee Shane H
Test Fit:
Shane H
Employee Robert C
Test Fit:
Robert C
Employee Conner L
Test Fit:
Conner L
Employee Ryan G
Test Fit:
Ryan G
Employee Bradley B
Test Fit:
Bradley B
Employee Mike L
Expert Research:
Mike L
Employee Robert G
Expert Research:
Robert G
Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Adam R
Expert Research:
Adam R
Employee Lori W
Expert Research:
Lori W
Employee Jeffrey L
Expert Research:
Jeffrey L
Employee Andrew K
Video by:
Andrew K
Employee Andrew L
Video by:
Andrew L
Employee Alan C
Video by:
Alan C
Employee Jonathan Y
Video by:
Jonathan Y
Employee Michael B
Video by:
Michael B
Employee Jeff D
Video Edited:
Jeff D
Employee Joshua S
Video Edited:
Joshua S
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Video Edited:
Kathleen M
Employee Dustin K
Video Edited:
Dustin K
Employee Sue W
Video Edited:
Sue W
Employee Chris R
Video Edited:
Chris R
Employee Zach D
Video Edited:
Zach D
Employee Cole B
Installed by:
Cole B
Employee David F
Installed by:
David F
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B

At 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.

Product Experts Available Now!
Call 1-800-940-8924