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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 # C56338
Our Price: $36.21
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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 into OEM tow package wiring harness. Powered converter reduces strain on wiring system. SMT construction ensures superior performance. 1-800-940-8924 to order CURT custom fit vehicle wiring part number C56338 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 (64)
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CURT Custom Fit Vehicle Wiring - C56338

  • 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 into OEM tow package wiring harness. Powered converter reduces strain on wiring system. SMT construction ensures 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 T-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
  • 1-Year limited 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, and scuff panel to access this harness. Once you've plugged in the connector, open your fuse box and locate the fuse position indicated in the instructions. Then insert the included 15-amp fuse.

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.

56338 Curt T-Connector - OE Replacement 4-Flat - Surface Mount Technology

Installation Details C56338 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 - C56338

Average Customer Rating:  5.0 out of 5 stars   (64 Customer Reviews)

Quickly and easily install a 4-way trailer connector on your vehicle with this custom harness. T-connector plugs into OEM tow package wiring harness. Powered converter reduces strain on wiring system. SMT construction ensures superior performance.

2019 Mazda CX-9

Pretty straightforward on this one. Exactly as advertised. Instructional video on the website was spot on. Very easy. Lil disassembly, plug in, put back together. Got trailer lights!


Easy for install especially with the short video.

2018 Mazda CX-9

Easy plug and play

2020 Mazda CX-9

plug and play. easy to use and install


arrived without issue. installation was simple.

2018 Mazda CX-9

Part got here on time, and fit easily, even easier than the video due (I think) to Mazda putting the ground wire in the connection. All I had to do was put the connector in, then test it. Worked great. My car is a 2018, and the video is for a 2016, but it is the same as far as taking the panels off.

Steve D.


Great, no problems.

2017 Mazda CX-9

Ordered a trailer hitch and wiring harness for my Mazda CX-9. Complete order received in just a few days, instructions were accurate and easy to follow, installed both the hitch and wiring harness by myself in 2.5 hours. Very satisfied. P.S. trailer installation video was very helpful.


The wiring harness was easy to install and works great. My only hiccup is that the install video does not exactly match the harness. Mine came with no need to run the ground wire. It is already wired directly into the loom. Also, instead of running the harness through the trunk and leaving it in trunk, I drilled out a plastic grommet next to the car’s harness and ran it out and down the inside of the rear quarter panel.


Plug and play! Super easy and clean way to get trailer lights added to car like factory setup.


No way this could be easier . Plug it in to the Mazda factory harness for the CX9 Signature and done.


Easy to install and it works!

2019 Mazda CX-9

As always, etrailer delivers!! Bought from them many times in the past and they never fail to deliver a top notch product at the best prices and the staff is very knowledgeable . . . BUY with confidence!!

2020 Subaru Outback Wagon

Plug for this device was well hidden behind the rear passenger interior trim. Finally found it but it was not as ‘accessible’ as I would have thought. Grommet under the spare tire is perfect for running the trailer plug through


Item came as described. Installation was made manageable with video instructions.


Instructions were clear, and the product has worked flawlessly.


Took time but easy to install myself with trailer videos. Has worked excellent.


Super easy install. Watch the videos! Other places say to hang it out the trunk, but there's a grommet under the spare tire.

2020 Mazda CX-9

Written instructions aren't great - but video is clear. Nice to have this vs. cutting factory wires.

2018 Mazda CX-9

Super easy install, plenty of supplied wire length, excellent available install videos. Do it yourself and save a bundle.


Plug and play great quality products

2017 Mazda CX-9

As usual, perfect fit. Thanks etrailer.


After a year, everything's as good as the day I installed it. No problems whatsoever on my Mazda CX-9.


Plugs right in, works like a champ. Video was great, a real time saver


Great product

Easy install. Very


Show More Reviews

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

  • Ground Wire on Curt T-Connector for 2018 Mazda CX-9
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56338 does not have a separate ground wire outside of the connector. You do not need to find an additional ground you will simply utilize the integrated ground in the quick connect just like the power for the converter. It is simply a plug and play harness. Connect quick connect to vehicle side harness, mount the converter, and run the 4-way to your desired location...don't forget the fuse on the power wire.
    view full answer...
  • Where Does the 15-Amp Fuse for the Curt T-Connector Wiring Harness Go?
    I believe the fuse referenced on your Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56338 is the fuse that goes into the fuse holder on the power (red) wire. I would check there first and see if the fuse has blown which sounds like it may have if all your wiring is good and you're still getting no power. If it has blown, simply replace the 15-amp fuse with another and check for functionality. If you're still having issues after checking this, come back...
    view full answer...
  • Trailer Wiring and Hitch that Fits 2022 Mazda CX-9
    We have trailer wiring that fits your 2022 Mazda CX-9 with the Tekonsha kit part # 118278 but the Curt you mentioned is not a fit for your vehicle. This will work great with the Draw Tite hitch you plan on installing on your vehicle as well # 76020.
    view full answer...
  • Tongue Weight Limit of 2019 Mazda CX-9 With Curt Trailer Hitch C13284
    You are always limited to the lowest-rated component, whether that is your vehicle - in your case a 2019 Mazda CX-9 - or the equipment. So I took a look at the owner's manual of your '19 CX-9 and it says the max towing is 3,500 lbs like you mentioned, but didn't specify a max tongue weight, just that it needs to be 10% - 15% of the trailer weight. So your tongue weight can be more than 350 lbs on your '19 CX-9, and up to 525 lbs with the Curt hitch that fits: - Curt Trailer Hitch Receiver...
    view full answer...
  • Recommendation for Adding a 5 Flat to Activate Surge Brake Reverse Lockout
    To get a 5 flat harness, like # 20036, installed, you will definitely want to be careful while installing. You will need to use a tester, like the # PTW2993, to make sure you are connecting to the correct wire. Once the correct sire is found, splicing is pretty easy with the included quick splice connector. The 60-inch wire also covers just about any vehicle.
    view full answer...
  • 4-way Wiring Harness for a 2021 Mazda CX-9
    Your 2021 Mazda CX-9 comes with a factory OEM tow package. Essentially all this is, is a plug in port that allows you to plug in the wiring harness instead of having to splice it into your wiring. Both the T-One Vehicle Wiring Harness for Factory Tow Package # 118278 and the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56338 will install using that OEM port and provide you with a 4-way trailer connector. While both wiring harnesses are a good option, I...
    view full answer...
  • Wiring Harness and Hitch Recommendation for 2016 Mazda CX-9
    The term 'Towing Package' is pretty useless because it's an extremely vague description whose meaning varies from vehicle manufacturer to vehicle manufacturer, and even among different models from the same manufacturer. For the sake of this discussion in terms of a wiring harness, Tekonsha uses the term 'tow package' because there is a single, dedicated connector for connecting a trailer harness, rather than installing inline where the factory taillight harness connects to the taillight...
    view full answer...
  • Parts Needed to Install 7-Way on 2022 Mazda CX-9
    To install a 7-way on your 2022 Mazda CX-9 you would first need to start with a 4-way like the Curt # C56338 which is a custom fit kit that doesn't require splicing. If the 7-way only needs to support trailer lighting function (not brakes) then all you need to convert it to a 7-way is the part # 37185 which plugs right into the Curt 4-way and is ready to go. If you need to operate trailer brakes the 7-way adapter you'd need instead is the # ETBC7 and a brake controller like the Tow Pro...
    view full answer...

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

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 Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video by:
Dustin K
Employee Jonathan Y
Video by:
Jonathan Y
Employee Cole B
Installed by:
Cole B
Employee Wilson B
Updated by:
Wilson B
Employee Isabelle B
Updated by:
Isabelle B
Employee David F
Test Fit:
David F
Employee Bradley B
Test Fit:
Bradley B
Employee Kristina F
Written by:
Kristina F

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