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  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 # C56040
Our Price: $34.58
You Save: 42%
Custom Fit Vehicle Wiring

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Shipping Weight: 0.92 lbs
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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. 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.
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  • Reviews (2329)
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  • Used (1)

CURT Custom Fit Vehicle Wiring - C56040

  • 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

Installation Details C56040 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Satisfaction Score:

Customer Reviews

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - C56040

Average Customer Rating:  4.9 out of 5 stars   (2329 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.

2023 Subaru Outback Wagon

Everything arrived in great condition and a lot sooner than I expected. I was even able to install it over the weekend.

I love the way most of the hitch is tucked away, out of sight. Can't wait to tow my boat and get back on the water.

The trailer wiring harness was super easy to install and tuck's away while not in use.

All in all, I am super satisfied with the whole experience. From the high quality of the product, timeliness of delivery, and minimal or low level of effort to stall the whole thing.

Thanks for everything. I attached some before and after photos.

2023 Subaru Ascent

Still have yet to test it out but it seemed to plug in fine. I didn't like the method of pinching the cable on the rear hatch when in use since I wanted to keep the harness mounted on the hitch at all times so I referred to a different install video that showed me how to run the wires through a grommet in the rear of the vehicle.


I am very pleased with the results. It went a lot faster once the wiring connector at the left tail light was located. It would have saves a lot of time and frustration if a picture could
be included With an arrow pointing to the correct connection. It also would have helped a lot if I had ordered the correct kit but to start with, but they were excellent in sending the correct kit and refunding for the first one.

2023 Subaru Outback Wagon

Like the product eliminates cutting and splicing factory wiring. Wish I had the instructions and or video for the 2023 Outback included with the harness. It would have saved me a couple hrs labor

2022 Subaru Forester

It is a really great hitch. And the installation was pretty easy. It only took me about an hour and a good part of that time was spent removing and installing the exhaust system and the worst part was the dust / dirt cover on the driver side of car.

I also bought and installed the trailer wiring harness pigtale . It was very easy once I located the connector on the car. That was hard to find because was not in the normal place for a Forester.


This is the second hitch assembly for my Subaru outbacks (2023-2024) very easy installation, Very little trimming needed. Easy removal of rear bumper cover then quick replacement of bumper bar assy to trailer hitch assy. Very fast service with free shipping.


Price was good but the Hitch came torn through the box and the coating removed and even what did not go through the box on delivery was chipped as well. no other packaging was put in the box so the tester and cable harness box could bounce around and move in box. I called customer service to return the hitch due to the damaged coating and they told me to clean it with soap and water and paint it. When I said I did not find that acceptable, she immediate told me that is how they all are and it is from stacking at the warehouse and she offered me a $[XX]paint credit to my card. Be warned! It did install easily by instructions and utube video.

2023 Subaru Crosstrek

Watched the video on the website how to install which made the install very easy. Have yet to test it but looks good and ready to go.


Straight forward and easy installation. Video was very descriptive.

2014 Subaru Outback Wagon

Easiest tail light converter that I've ever put on a vehicle Everything went perfect


Good product. I especially appreciated the video put out by etrailer for the installation. It made it into a simple installation - and the recommendation to keep the harness inside the car unless pulling the trailer was a real bonus, no need to mount on the outside.

2024 Subaru Crosstrek

It fit very nicely. I found the factory plug at the rear threshold, about 14" left of the door each point.

Unfortunately the 4-pin connector end didn't fit through a factory hole to the outside without a little widening of the hole.

2022 Subaru Forester

Installation went very well. I watched your online video first which was very helpful. Took about three hours because I did it alone in my driveway so had to create ways to hold up hitch while I started installing nuts. Also went slowly so I wouldn't make mistakes. If I had to install another one it would probably take half the time or less with a helper.


The YouTube instructional video helped and made this installation very smooth. perfect fit and it looks great!

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.

2014 Subaru Forester

Works perfectly and the installation video made it a breeze to install.

2023 Subaru Crosstrek

This went in VERY easily and makes for a clean install. Only reason it’s a 4 is that the (tiny) self tapping ground screw stripped out before I got enough torque on it to make a reliable connection (with a human powered screwdriver). I just used a 10 or 12 sheet metal screw that I had in the screw jar. I’d recommend using the provided small screw to drill a pilot hole and then follow up with something bigger. All things considered I recommend this.

2023 Subaru Crosstrek

Great product. Relativly easy to install. I did I by myself with the use of a motorcycle jack stand to lift the hitch up into place an tight it down.

2023 Subaru Forester

Would give 5 star if the box wasn't all torn up & slight scuff on hitch. I also got a hitch 2 months ago with the same results. Need to do a better job of packing your stuff. The information & videos as always are great along with the pricing. Don't know if I'll try another place for my next order.

Etrailer Expert

Katrina D.


I am sorry that your hitch arrived with some scuff marks, not only once but twice now. I highly recommend covering up those scuffs with some rust-o-leum type of paint, to prevent any corrosion. As for the poor shipping situation, let me get you over to customer service to see if there is anything we can do to correct this poor experience.

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.



Fantastic! High quality components and great instructions!


This is my third time ordering from etrailer. Parts always fit, easy to install if you follow their videos. Would recommend this item, and ordering from this site.

2024 Subaru Outback Wagon

Website was easy to navigate when searching for and ordering a trailer hitch for my new car. checkout was straightforward. Parts arrived quickly. Instructions were clear and succinct.


Very easy to install on my '22 Subaru Outback. I didn't bother running it out of the hatch area though. I just pull it from under the mat & hang it out the back when needed. Great!

2019 Subaru Forester

I'm a fan of drawtite products and though I'd give etrailer a try. The etrailer receiver was cheaper than the drawtite one and was also made in USA. Professional welds and a nice power cote paint job. I'll give it 5 stars.

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.

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

Condition: Like New

Notes: May have damaged packaging or minor cosmetic blemishes.

Our Price: $32.51
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