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  1. Custom Fit Vehicle Wiring
  2. CURT
  3. 4 Flat
  4. Trailer Hitch Wiring
  5. No Tow Package
  6. Vehicle End Connector
Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
CURT

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

Part Number: C56404
In Stock
$87.86
Retail:$147.95
You Save: 41%
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 C56404 or order online at etrailer.com. 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 (65)
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CURT Custom Fit Vehicle Wiring - C56404

  • 4 Flat
  • Trailer Hitch Wiring
  • No Tow Package
  • Vehicle End Connector
  • CURT
  • Plug-In
  • Powered Converter
  • Plug and Lead
  • Hidden

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.


Features:

  • 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 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


Specs:

  • Maximum amperage:
    • Stop/turn lights: 5 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • Limited 1-year warranty


Installation

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 covers, storage trays, sub woofer, spare tire, scuff panel, and interior side 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 trunk.


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.



56404 Curt T-Connector - Surface Mount Technology - 4 Wire

Installation Details C56404 Installation instructions

This Product Fits The Following Vehicles



California residents: click here


Customer Satisfaction Score:

Ratings & Reviews

4.6

65 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.

by:

I installed the Curt trailer wiring kit right after I installed my hitch, so some of the access points were already open. If you follow directions and install the converter in the battery compartment, the wiring harness to the tail lights will be too short. I installed the converter in the driver side compartment where the air compressor rides and ran the power wire only to the battery compartment. This provided barely enough length to reach the tail light wiring connectors in the lift gate. Other than that, I followed the directions and everything looks good, all the wiring is hidden behind trim panels, and the harness works great.

Bob profile picture

Bob

7/26/2022

Easy as advertised and I still like it.



by:

Everything worked with Audi's electrical system.
Outstanding!



by:
Audi

Perfect fit for my 2013 Audi Q5



by:
2017 Audi Q5

Very easy install after watching the excellent instructional video.



by:

Watched the video before it arrived, went together without any issues, just make sure you reinstall the bottom trim that has the sensor before testing for power at the plug, there won’t be any power if you have put that trim piece installed



by:
2016 Audi Q5

Video instructions are great. Installed it in my 2016 Audi Q5 within a couple hours. It works and is hidden when not in use. Would be five stars if the ground wire was long enough to reach the battery. I used an existing bolt to the body for ground, not the included self tapping screw The 4-way light tester is not included, but I was able to get one locally.



by:

Still working flawlessly! Watched the YouTube videos by etrailer and it made the install easy and quick. Love things that work right the first time with zero issues.



by:

Made the install really easy.

Daniel profile picture

Daniel

11/1/2024

Wiring set made the installation process a breeze. Works really well and provides a strong signal



by:
Audi

Works great, a little more in depth than some other vehicles but what isn’t on an Audi. It’s worked great for me so far



by:

The wiring harness didn't work.

Gwendolyn Y. profile picture
Etrailer Expert

Gwendolyn Y.

4/29/2025

Hey Thomas. I'm sorry to hear that the harness didn't work. Were the plugs not right or are you having power issues? I want to help out so you have a working harness for your trailer. Let me know when you can.

Thomas profile picture

Thomas

5/2/2025

@GwendolynY I am having a power issue. Not getting any light signals. My next step will be to check the ground and power connections.


by:

I did end up using it, but the install is ridiculous. I took it to the Dealer and paid ~ $500 to have it installed. The directions show routing the wires up side thru roof and into lift gate lites. And you have to dissasemble the lift gate door panels, Crazy. Even the dealer did something much simpler.

Jenny N. profile picture
Etrailer Expert

Jenny N.

3/22/2022

The installation for this harness is a detailed installation. I recommend downloading the manual from the product page as it will give step by step instructions so that you determine the difficulty.



by:

I have not installed it yet, but the order was delivered as promised and I like the fact that this item uses factory plugs instead of splicing or tapping into wires.



by:
2017 Audi Q5

The harness was easy to install. I did need to purchase a 4 prong socket mount so it would not hang loose from the rear of the car.



by:

Be aware that the trailer lights do not work with the hatch open but otherwise easy to install and functions as intended.

Andrew profile picture

Andrew

10/18/2022

Still working as advertised, happy as can be.



by:
Audi Q5

Installation was decently straight-forward (as much as anything can be with an Audi) and sits nicely. I'm very pleased with how low-profile this hitch is. A great choice if you're looking to tow with your Q5. I will recommend accounting for how low the receiver is when you buy your ball hitch.



by:

I purchase the product and I try it and it was great. I didn't use it a lot of times but all the connectors was fitting very good and it is almost like factory one. That was my goal to be as closest as possible to the factory.



by:

Shout out to etrailer! Wanted to save some money and do the wiring myself so Ed hooked me up with the right stuff and with a quick tutorial from etrailer online showing a clever and effective shortcut, I had it installed in about 30 minutes. Thanks, the hitch I purchased also installed easy with the online help. 100% will use etrailer for all my trailering needs.



by:
2015 Audi Q5

Product is great, instructions are well done. When installing however, the driver's side wiring was not long enough to mount the unit in the battery well as depicted in the instructions, and the passenger-side wiring length only allowed the wiring to be routed under the trim along the top of the hatchback (not along the scuff plate at the back of the car). The CURT instructions should be updated to make this clearer.



by:

The installation instructions are not detailed enough. Other than that, all good. Easy to install



by:

This harness uses factory original plugs that interface with the vehicle's original wiring harness to make installation a breeze, quite straightforward and seamless. No janky scotchlocks, crappy crimps or poor "splice" jobs to be had here. Some disassembly required, but all the best wiring jobs do. 100% would recommend for the professional installer, although this project may be above the heads of the inexperienced DIYer.



by:

All in all, it was a very simple install for both the hitch and the lights. Would highly recommend. I do think they could have packaged it a little better, it broke through the box in shipping, but it’s a heavy hitch, so it is what it is.



by:

Flawless instructions and has worked great for over a year! Needs a bracket for the plug!



by:

Installation was easy and it works as advertised. The power wires were a little short and needed to be lengthened. That wouldn’t stop me from purchasing again.



by:

Works as advertised. Pretty simple install. As usual great quality product(s) from etrailer



by:
2015 Audi Q5

Have not installed yet but looks to be an easy install as instructions seem to be pretty clear


25
65
Show More Reviews

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

  • Curt 4-Way Not Operating Left Turn Signal On 2014 Audi Q5
    You are going to want to start by checking inside the connectors on the Curt T-Connector Vehicle Wiring Harness # C56404 to verify if any of the pins were bent or pushed out on the connectors. You can also use a Test Light # PTW2993 to test both the power going into the power converter from the different functions and verify the power coming out of the converter as well to verify if it is damaged and would be able to be replaced under the manufactures warranty.
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  • What is Needed to Use Curt Echo Brake Controller on 2017 Audi Q5 With 4-Way
    Hey Larry, Since you already have the Curt 4-Way # C56404 installed on your 2017 Audi Q5, you're halfway there for what you need in order to install and use the Curt Echo Brake Controller # C51180. The other part you'll need for the Echo is the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation # ETBC7L. This will give you the necessary wiring and 7-way connector for your Audi to use the Echo.
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  • Will Trailer Hitch Weaken Bumper of 2015 Audi Q5
    That's a good question but no, the bumper on your 2015 Audi Q5 will not be damaged more easily and will not be more fragile with the installation of the Draw-Tite Max-Frame Trailer Hitch Receiver # 75940. The bumper support is directly replaced by the hitch, and in fact the bumper support is made of aluminum while the hitch is steel. So the hitch won't negatively affect you (or your pup getting in and out) of your Audi. I also wanted to add that if you plan on doing some towing and need...
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  • Can Prodigy P2 Brake Controller Install in 2015 Audi Q5
    Yes you can install a Prodigy P2 part # 90885 in your 2015 Audi Q5 that currently does not have any trailer wiring. For that you would need to start with a 4-way like the part # C56404 which installs easily and does not require hardwiring to the vehicle. Next you'd just need the part # ETBC7 which comes with everything needed to convert the 4-way to a 7-way and wire in a brake controller.
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  • Is There a Trailer Hitch Receiver Rated For Weight Distribution For a 2016 Audi Q5?
    As the Draw-Tite Max-Frame Trailer Hitch Receiver # 75940 and all of our other receivers for your 2016 Audi Q5 are not rated for use with a weight distribution hitch this leads me to believe your chassis cannot support the use of a weight distribution hitch. While I could not find any specific information to confirm this the only mention I see of it in your owners manual is to referring to the loading of luggage between your vehicle and trailer when towing. The 4-Way Harness # C56404...
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  • Recommended Hitch and Wiring Harness for a 2016 Audi SQ5
    I would be happy to help you. For a Draw-Tite Hitch on your 2016 Audi SQ5 you will want item # 75940. This hitch is custom fit and bolts directly to your Audi's frame with included hardware. To add a brake controller you will need two separate wiring harnesses because you will need to add a 7-way to plug the trailer into. The first harness you will need is the Curt T-Connector item # C56404. This custom-fit T-connector plugs into your vehicle's wiring harness, which is located in your...
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  • Passenger Side Taillight not Illuminating After Installing Curt Wiring On Audi Q5
    It sounds like you have a classic ground issue with the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer part # C56404 on the 2016 Audi Q5. When the wiring harness does not have a good ground connection it will make the functions act erratically. Some functions will illuminate while others won't. I recommend to take a look at your ground connection and make sure it is attached to a clean bare metal surface of the vehicle's frame. Also please keep in mind this wiring harness...
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  • Trailer Wiring that Fits 2014 Audi Q5
    Yes we have trailer wiring harnesses that fit your 2014 Audi Q5 like the Curt # C56404 which installs easily by plugging in line with the taillight wiring of the vehicle.
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  • Installing 7-Way Connector and Brake Controller on my 2014 Audi Q5
    If you currently have a working 4-Way plug then using the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation Kit part # ETBC7 kit is a great way to get a powered 7 Way connector on the rear of your 2014 Audi Q5. You can use the Curt No-Drill Bracket part # C57202 to attach the 7-Way to. The bracket will mount around the tube of your hitch and really does a great job staying solid. With this kit using the Curt Echo part # C51180 is an easy way to add a brake controller that...
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  • Troubleshooting Curt Trailer Wiring Harness Installation on 2017 Audi Q5
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56404 is a confirmed fit for your 2017 Audi Q5 and fits behind both the driver and passenger side rear access panels. I've attached the installation instructions which gives you photos to see the locations. The wires will be long enough when installed correctly. I confirmed this with Curt.
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  • Where Does Trailer Wiring Store on 2015 Audi SQ5
    Not all trailer hitches have trailer wiring mounts on them like the Draw Tite part # 75940 that you referenced. I would even say that most actually do not. Especially on designs like the # 75940 where only the hitch opening hangs below the rear bumper. There just isn't a convenient and accessible place on the hitch for it to be. So in these situations if wiring does need to get mounted and doesn't store inside the vehicle hatch you would attach a bracket to the rear bumper fascia. The...
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  • Best Trailer Wiring Options for 2017 Audi Q5
    For your 2017 Audi Q5, yes, the part # 119250KIT would work. It is a no-spice install and comes with the power wire you'd run up to the battery. I attached an install video link for this for you to check out on a very similar 2018 Q5 as well. Not to make your choice any harder but we also have the Curt harness # C56404 which is custom fit instead of universal so it would also be a very easy install.
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  • Wiring Harness Fit For 2014 Audi Q5 Premium
    While we do have a trailer wiring harness for your 2014 Audi Q5 Premium, I checked with Curt and the part you mentioned is not a fit. Instead, the correct wiring harness for your Audi is the following: - Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56404 I verified with Curt that the # C56404 is compatible and will fit your '14 Audi Q5 Premium so you can power your trailer lights. It will work perfectly in conjunction with the hitch that fits your car,...
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  • Installation Process for Curt 13136 Hitch for 2014 Audi Q5
    Because of where all hitches are going to need to attach to on your 2014 Audi Q5, removal of the rear bumper is going to be a required step regardless of what hitch you're installing; unfortunately there's no way around this. While the process may seem daunting at first glance, it's not terribly complicated and when done with care and patience, you can avoid damaging the bumper. If you're going to be towing with this hitch, you'll also need trailer wiring, a ball mount, hitch ball, hitch...
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  • Adding 7-Way and Brake Controller to 2017 Audi SQ5
    Hey Mark! You already have the right idea here. To add a 7-way you will need to start by adding a 4-way. I recommend using the Curt T-Connector Vehicle Wiring Harness # C56404. This plugs into the connection points in the rear cargo area and then you will run a hot lead up to your battery. Once you have your 4-way you can use the # ETBC7 you looked at to upgrade to a 7-way. None of this will require splicing into the vehicle wiring. For a brake controller I'll give you two options. The...
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  • Does the Curt C56404 for a 2017 Audi Q5 Work w/ LED and Incandescent Trailer Lights?
    It will work with both. The Curt T-Connector Vehicle Wiring Harness item # C56404 sends the signals from your tail lights to the converter box that actually powers your trailer's lights. The direct line from the battery powers both LED and incandescent bulbs. The Curt T-Connector Vehicle Wiring Harness item # C56404 is confirmed to fit a 2017 Audi Q5 with the factory supplied connector located in your cargo compartment. If you do not have the factory connector you'll have to use the...
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  • Parts Needed to Install Redarc Tow Pro Brake Controller in 2023 Audi SQ8
    Hey Mark, so the trailer wiring you would have on your 2023 Audi SQ8 would be a 4-way since it's a sedan so to convert that to a 7-way and wire in a brake controller like the Redarc Tow Pro Liberty part # RED52VR you would just need the part # ETBC7 and you'd be set.
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  • How To Secure Curt Echo On 2015 Audi Q5
    The best option to secure a trailer connector on a 2015 Audi Q5 with a trailer hitch like the Draw-Tite Max-Frame Trailer Hitch Receiver part # 75940 is the Curt Easy Mount Bracket part # C58000. This will provide a safe and secure connection for the 7-Way RV Upgrade Kit part # ETBC7L and Curt Echo Wireless Trailer Brake Controller part # C51180. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part # C56404 is an excellent option as well.
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  • Trailer Wiring Harness Recommendation for a 2015 Audi Q5
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  • Will the Curt T-Connector Vehicle Wiring Harness C56404 Fit a 2013 Audi Q5 Hybrid
    The Curt T-Connector Vehicle Wiring Harness part # C56404 is a confirmed fit for a 2013 Audi Q5 Hybrid. It offers plug-n-play installation as well so there will be no splicing into any wires on the vehicle. It provides a standard 4-way flat trailer connector that has all the basic trailer lighting functions. If you don't already have a trailer hitch, the Draw-Tite Trailer Hitch Receiver part # 75940 is what I recommend because of the hidden cross tube. It offers bolt-on installation as well.
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  • Recommended Trailer Hitch and Wiring for 2014 Audi Q5 Hybrid
    I recommend using the Curt # C13136 on your 2014 Audi Q5 Hybrid, which will provide you with a 2" hitch receiver that is well suited for towing a trailer. It looks like your Q5 hybrid has a 4400-lbs towing capacity, so you'll want to make sure that you stay under that to avoid damaging your vehicle, but this hitch will allow you to tow up to that capacity. Since you're going to be towing, you'll also need trailer wiring, a ball mount and hitch ball to complete your towing setup. For wiring...
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  • Which Trailer Wiring Harness Fits 2014 Audi Q5 TDI
    Hey Michel, I am not sure how the guy in the video you found was able to install that trailer wiring kit on an Audi Q5 but it was not designed as a fit for your vehicle so it wouldn't work for you and you'd need to go with the part # C56404 instead. I wonder if he somehow got his part numbers confused or something.
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  • Parts Needed To Tow a Trailer With Brakes Using a 2014 Audi Q5
    In order to tow a trailer with a 2014 Audi Q5 you'll need a trailer hitch, trailer wiring harness, brake controller (if applicable), and ball mount/hitch ball. The Draw-Tite Max-Frame Trailer Hitch Receiver part # 75940 is a great option to start with. For the trailer wiring, the Curt T-Connector Vehicle Wiring Harness part # C56404 is what I would start with as it can then be adapted to a 7-way using the Trailer Brake Controller Install Kit part # ETBC7L. This setup will then work perfectly...
    view full answer...
  • Installation of Draw-Tite Trailer Hitch Receiver on 2017 Audi SQ5
    We haven't had the opportunity to make a video of the Draw-Tite Max-Frame # 75940 on a 2017 Audi SQ5 like yours as of yet. However, since the hitch fits both the 2017 and 2016, the installation will be very similar. I've linked a video of the hitch being installed onto a 2016 Q5. If you also need a 4-way wiring harness the correct part is # C56404.
    view full answer...


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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jameson C
Expert Research:
Jameson C
Employee Kathleen M
Video Edited:
Kathleen M
Employee Chris R
Video Edited:
Chris R
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
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Employee Ronnie R
Written by:
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Employee Jacob H
Test Fit:
Jacob H
Employee Ian F
Test Fit:
Ian F
Employee John S
Video by:
John S
Employee Daniel D
Video by:
Daniel D

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