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  4. Trailer Hitch Wiring
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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 # C56174
Our Price: $75.70
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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 C56174 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 (11)
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  • Videos (1)
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  • Why etrailer?

CURT Custom Fit Vehicle Wiring - C56174

  • 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 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. To access this harness, you will have to remove the rear scuff panel and pull back some of the trunk liner. 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.

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.

56174 CURT T-Connector - Surface Mount Technology - 4 Wire

Installation Details C56174 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 - C56174 Review

Today, we're going to review part number C56174. This is the CURT T-Connector Vehicle Wiring Harness with the 4-way flat trailer connector. Now, this part is a custom fit part. It is designed to fit the FIAT 500 models starting in 2012. Now, on any custom fit part, what I always recommend is to go to our website, use our fit guide, put in your year model vehicle, and it will show you inaudible 00:00:24 for your application. Now this part provides this 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights. Connects very quickly and easily.

Basically, you just locate your connection points in the rear cargo area, plus in this T-connectors, one for each side, ground your white wire, and then run your power wire to your vehicle's battery and you'll be all ready to go. Now this part does include this tail light converter, this black box right here, and this is to ensure that your vehicle's wiring will match that of your trailer. It is a power module converter, which means it connects directly to the battery using this black wire right here, and the reason they do that is to avoid overloading your vehicle's electrical system. Now this converter is constructed using SMT technology, which is surface-mount technology. Gives you a consistent, reliable performance, and it'll help maximize your trailer light yield and intensity while producing minimal heat, and it will also ensure us superior operation in any rough road conditions. Also comes with this nice dust cap for the 4-way, which is, notice, you can attach that to the plug and you can leave it on there if you'd like, and then, when you're not plugged in to your trailer, just put your cap over your terminals, protect those terminals of any elements are from any damage. A few specs on this harness. A maximum amperage for the stop and turn lights circuits is 3 amps per circuit.

On the tail light is 6 amps total. Now, this part comes with everything shown here on the table. Comes with a nice set of detailed instructions that'll describe how to install it, but also the nice thing is it gives you pictures of where the connection points are and helps install it. But briefly, when you go to install this, what you want to do is go to the back of the vehicle in the cargo area, and then gain access to behind the tail lights, and what you'll do is start on the driver's side, and you'll take this T-connector right here that has the yellow wire in it. That's for the driver's side, and you'll go ahead and unplug the harness behind the tail light. Key this into that, and then you'll notice there's a white wire that has an eyelet on it right here on the same wire. This you want to connect to a good clean ground if there's one nearby.

If there isn't, you can use this grounding screw to make it ground for you, then what you'll do is you take this other T-connector that has this length of green wire. That's for the passenger's side so you'll run this length of wire over to the passenger side, plug in this T-connector behind the tail light on the passenger side. What you want to do also is, this converter, you want to make sure it adheres to a nice, clean, flat surface or doesn't bounce around, so they do include a double-sided tape you can use to attach it, and also some extra cable ties to help secure it down also. Now, the last wire you have is this black wire. Again, this is the power wire, so this power wire needs to go to your vehicle's battery, which is in front of the vehicle. What you'll do is you take this length of wire they include, have the two ends on it.

You'll take the included butt connector, put it on the power wire, and then connect it to one end of this length of wire, and then with that all connected, you'll run this wire to the front where the battery is. Use them with a cable ties to take up any slack or to hold your wire up. Once you get up by the battery, you don't want to connect this directly to the battery. You want to run it through this inline fuse holder. Again, take the other included butt connector and attach it to one end of the inline fuse holder just like that, and once that's all connected, you have your one side here that you'll need to take the included eyelet holder, or eyelet connector. Attach that, and then this will connect to the positive post of your vehicle's battery. Once that's all connected, just pop open the cap, take the included 10-amp fuse. Go ahead and put it in the fuse holder, put the cap back on it, and then your system should be all ready to go, so go to the back, run your 60-gauge bonded wire that the 4-way is connected throughout the back, plug it in to your trailer. Once you plug it in, you'll have lighting on your trailer all ready to go, but that should do it for the review in part number C56174. This is the CURT T-Connector Vehicle Wiring Harness with the 4-way flat trailer connector.

Customer Satisfaction Score:

Customer Reviews

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - C56174

Average Customer Rating:  4.8 out of 5 stars   (11 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 new "plug & play" version to the outdated wire splice type. Solid and dependable. Exact fit for our Fiat. Using the system currently. 5 Stars.

2013 Honda Element

What makes this hitch system a sure winner is the absolute ease and accuracy of the installation. The video is an outstanding addition to walk you through almost everything. I say almost, because the one missing element is a 'how-to' on installing the positive lead to the battery. I'm still wrestling with whether or not to run it internally or externally. Aside from that, I was able to put the rear of my 2013 Fiat Abarth on solid stands which gave me ample room to do everything. Although the video suggested pulling additional supports off of the exhaust system to make it easier, I found that it wasn't necessary (and besides, since the car wasn't on a lift, as in the video, accessibility was a bit tougher). The entire installation took about an hour because I was pausing periodically to watch the video and make sure I wasn't missing anything. Someone more mechanically skilled could probably do this in less than 30 minutes. Well done, etrailer!

2012 Fiat 500

Well made, easy to install and worked perfectly.. We just sold the car and I removed the wiring harness so I can install it in our next fiat.. Highly recommend this product. Mahalo


Easy installation with the exception of routing the hot lead to the battery. A recommended path would be an improvement here as the coil springs must be avoided.

No problems.
Michael S - 05/19/2018


It's very easy to hook up I'm glad I bought it works great no problems

2013 Fiat 500

In my case, it arrived securely packaged within the Hidden Hitch box. At the writing of this 'review' - I haven't installed it yet. TBD.

2013 Fiat 500

Good part. I bought this for my van and works well.


works just like the package says. easy install

2012 Fiat 500

easy install, works great!

2012 Fiat 500

2015 Fiat 500



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

  • Wire Colors on the Curt T-Connector Vehicle Wiring Harness Part # C56174
    In regards to the Curt T-Connector Vehicle Wiring Harness part # C56174 which is a fit for a 2012 - 2018 Fiat 500 and a 2012 - 2017 Fiat 500 Abarth, the wire colors after the converter are as follows: Green: Right Turn/Stop Light Yellow: Left Turn/Stop Light Brown: Running Light White: Ground The t-connector with the yellow wire will go to the driver side tail light housing and the t-connector with the green wire will go to the passenger side tail light housing.
    view full answer...
  • Curt Receiver Hitch and Wiring Harness for a 2013 FIAT 500 Sport Cattiva
    Yes, the Curt Trailer Hitch Receiver Custom Fit Class I - 1-1/4" item # C11363 is a confirmed fit for your 2013 FIAT 500 Sport Cattiva. The Curt Receiver Hitch is a confirmed fit for all models except the Abarth of the 2013 Fiat 500. That receiver's maximum gross trailer weight is 2,000 lbs and the maximum tongue weight is 200 lbs. I recommend the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector item # C56174. This harness plugs inline with your rear tail lights...
    view full answer...
  • Trailer Wiring Harness for Fiat 500 and Tail Light Isolating Converter for Trailer 3-Wire System
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56174 will still be what you need for your vehicle. The adapter you need for your trailer will actually be on the trailer side. I recommend the Curt Vehicle to Vehicle Tail Light Converter # C56196 which will separate the combined turn and stop light signals for your trailer function. You will want to use a diode like # 38955 on the tail light function to prevent power feedback.
    view full answer...
  • Trailer Hitch Recommendation for a 2016 Fiat 500X
    I checked with Curt and the trailer hitch part # C13271 that you referenced has been confirmed as a fit for all models of the 2016 Fiat 500X so it would work well on your all-wheel drive model. If you wanted to do some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4 inch rise or 4 inch drop. It also includes a 1-7/8 inch ball, 2 inch ball, hitch pin with clip, and a storage bag. If...
    view full answer...
  • Is Curt 4-Way Wiring Harness Compatible With 2017 Fiat 500E
    That's a really good question, so I checked with Curt for you and verified there are no restrictions on their wiring harness, and it is absolutely compatible with your 2017 Fiat 500E; the harness that fits is the following: - Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56174 So you can use this harness without any issue with your '17 Fiat 500E, and if you also need a trailer hitch for this vehicle, I went ahead and verified for you that Curt has a hitch...
    view full answer...

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Info for this part was:

Employee Lindsey S
Written by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Wilson B
Updated by:
Wilson B
Employee Hannah L
Updated by:
Hannah L
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B

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