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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 # C56377
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Custom Fit Vehicle Wiring

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C56377 - Powered Converter Curt Trailer Hitch 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. Call 800-298-8924 to order Curt custom fit vehicle wiring part number C56377 or order online at etrailer.com. 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.
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  • Reviews (18)
  • Q & A (26)
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  • Why etrailer?

Curt Custom Fit Vehicle Wiring - C56377

  • Custom Fit
  • Trailer Hitch Wiring
  • Curt
  • 4 Flat
  • Powered Converter

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 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


Specs:

  • Maximum amperage:
    • Stop/turn lights: 3 amps per circuit
    • Tail lights: 6 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 floor coverings, storage trays, rear scuff panel, and side trim panel 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 rear 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.



56377 CURT T-Connector Vehicle Wiring Harness with 4 Pole Trailer Connector

Installation Details C56377 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 - C56377

Average Customer Rating:  4.8 out of 5 stars   (18 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.

- C56377
by:
2019 Mazda CX-5

Same as trailer hitch. Best for all my needs new car so added wire harness 605081



- C56377
by:
Mazda

I have not installed yet, but I installed another harness on my 2016 Mazda and it worked extremely well. I am sure this will work just as well. Shipping was fast and easy. Great company, price and product. Will definitely buy again when I need to. 607570



- C56377
by:
Mazda

Everything is easy to install except the line to the battery, and that just takes patience. I ended up temporarily removing the driver’s side protectors for an easier and cleaner run up my 2018 Mazda CX-5. 541743


Comments
One year out and Im still very pleased!
Scott - 07/14/2019

57802

- C56377
by: 10/02/2020

896096



- C56377
by:

Easy install. Watched the videos and removing the panels was easy. Ran the wire up to the batter without problem under the car, under the protective covers. Its tucked up nicely and I know it will not get caught or damaged on anything. 893911



- C56377
by:
Mazda

Works well. Running hot wire is a pain, but that is a mazda problem. 884034



- C56377
by:

Everything was as advertised. Easy to follow instructions and correct fit. 893158



- C56377
by:
2020 Mazda CX-5

Purchased a Class III Hitch Receiver and wire harness for a 2020 Mazda CX5. Arrived within a couple of days, was well packaged and complete. Hitch installed fine and planning to install wire harness this weekend. 849568



- C56377
by:
2020 Mazda CX-5

I installed this wiring harness myself on my 2020 Mazda CX-5. The instructional video was REALLY helpful. It showed in detail how to remove the interior panels to gain access to both taillights. The plug in T-Connectors were a snap to plug in. I chose to run the wire to the battery beneath the vehicle but inside the under sound proof panels so the wire is almost completely hidden from the elements. Works great and I would highly recommend this wire harness for a 2020 Mazda CX-5 (I think it works for earlier models as well) 831344



- C56377
by:

Very good construction, just like it was advertised, fits perfectly. I am very happy with it! 820378



- C56377
by:
2019 Mazda CX-5

Great instructions and easy install. 803306



- C56377
by:

Good solid product. Better than portrayed in advertisement. Directions and hardware better than expected. Included some tools I wasn’t counting on. Product support the best. A +. 705591



- C56377
by:
2019 Mazda CX-5

Installation was clear and concise except for the battery lead. Don't know if it goes inside or outside. The rest was easy. 672580



- C56377
by:

Excellent product, easy installation on a 2018 Mazda CX-5 except for the hassle overcoming snaking the source wire through Mazda's difficult undercarriage. Worked perfectly after completed. 667657



- C56377
by:
2018 Mazda CX-5

Not a bad install, it was kind of fun. But, in the video I watched they failed to mention the hardest part: running a 12ga, 12V wire from the battery to the rear of the car. It was a little scary drilling a hole in a brand new car's firewall to get the wire through (I did not want to run it under the car, that seemed much sketchier than running it through the interior.) But I hooked it all up, connected my trailer, and, perfect: all lights work great. 550831



- C56377
by:
2017 Mazda CX-5

I am returning this because it is supposed to be plug and done. Well, I had to route a wire from the battery to the back of the vehicle. I found another one that doesn't require that step and draws power from the back junction box. Easier. 510674



- C56377
by:

Excellent Quality Fast Shipping. Have not installed Yet. Not looking forward to disassembling the Automobile to Install this. 466375



- C56377
by:

Ordered trailer hitch receiver on Sunday, received in 3 days with free shipping. Great installation information on their website. Super customer service, email and phone call received day after ordering to confirm my order and next day when it shipped. 432452


18
18

Ask the Experts about this Curt Custom Fit Vehicle Wiring

  • Where are Connectors on 2020 Mazda CX-5 to Connect Curt 4-Way Wiring Harness
    If you take a look at the cut out I added of the linked installation instructions, you can see that the connectors for your 2020 Mazda CX-5 are located behind the trim panels on the sides of your vehicle. These are the taillight wiring harnesses that you will connect to the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56377. Along with the 4-way, to complete the towing set up on your 2020 Mazda CX-5 I recommend the Curt Trailer Hitch Receiver - Custom...
    view full answer...
  • Why Does Trailer Wiring Harness for 2017 Mazda CX-5 Require Running Wire to Battery
    Not all vehicles can handle the additional amperage draw of the trailer taillights on the vehicle taillight circuits. Those vehicles need setup that draws power from the battery. Some vehicles have higher rated circuits that can handle this, and others need to have the power drawn straight from the battery to protect the taillight circuits. For your 2017 Mazda CX-5 you need to install a harness that draws power from the battery to protect the taillight circuits. For that you would need...
    view full answer...
  • Does Wiring Harness on 2019 Mazda CX-5 Have to Get Power From 12V Battery
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56377 will always be connected to a battery so it will be "on" in the same way that everything else that is connected to the battery of your 2019 Mazda CX-5 is "on." That said, there are no negative effects, problems, or issues whatsoever with it being connected to your Mazda's battery. The only problems that will arise are from attempting to power the connector from anything but a direct hot lead to the...
    view full answer...
  • Does Curt Trailer Wiring for 2020 Mazda CX-5 have to Wire to Vehicle Battery
    We can't recommend you use any power source for installing the Curt # C56377 other than the positive post of the battery. This allows you to completely bypass the wiring of the vehicle so that in the event of a trailer wiring short it doesn't hurt the vehicle wiring.
    view full answer...
  • Options for Running Power Wire of Curt Trailer Wiring Harness # C56377
    The connection to the battery is something that many people have reservations about until they actually start the process and realize that it is not so bad. There are different ways you can get to the battery and we actually wrote an FAQ article on this topic which I have linked for you. The FAQ gives general tips on different methods for routing the power wire. You can run the wire through the vehicle if you wish but just keep in mind that this does take more time and you may end up...
    view full answer...
  • Easy to Install Trailer Wiring Harness for 2020 Mazda CX-5
    I checked with Curt and they just recently confirmed the fit of their trailer wiring harness # C56377 for your 2020 Mazda CX-5. This is a custom install kit so the install would be super easy as well!
    view full answer...
  • Trailer Wiring Harness Recommendation 2020 Mazda CX-5
    Tekonsha and Curt both offer trailer wiring harnesses for your vehicle. Between the Curt # C56377 and the Tekonsha # 118746, I'd suggest the Tekonsha, as it has a higher amperage rating at a pretty similar price. If you click the provided link, you can see a video of the harness being installed.
    view full answer...
  • Troubleshooting 3rd Brake Light Not Working on 2019 Mazda CX-5 After Installing Curt T-Connector
    You might want to go back through and trace the steps that you took when installing the Curt T-Connector # C56377 on your 2019 Mazda CX-5 to see if you accidentally forgot to plug something in or if maybe some wiring got damaged. Since the tail lights are working properly I don't see how the T-Connector would be affecting the 3rd brake light but if everything looks fine you might as well disconnect the tees from the Curt wiring harness and plug everything in like it was prior to installation...
    view full answer...
  • Does Curt Trailer Wiring Harness # C56377 Have Label On It
    The Curt harness part # C56377 does not have a label on it. Thank you for the picture but what you have is correct! I checked your order notes and you received the correct harness too.
    view full answer...
  • How To Tow Trailer with Separate Stop/Turn Signals Using a 2018 Mazda CX-5
    In order to tow a trailer using separate brake and turn signal circuits with your 2018 Mazda CX-5 you will first need a standard 4-way trailer wiring harness, the Curt T-Connector Vehicle Wiring Harness part # C56377 which is plug and play. Then, in order to attach the trailer to this connector you will need to install a converter in between the trailer lights and trailer side trailer connector, the Vehicle to Vehicle Tail Light Converter part # 118158 along with a trailer side 4-way, the...
    view full answer...
  • How to Test to Determine if Trailer Wiring Converter Box is At Fault
    Yes, it is possible that the converter box of your trailer wiring kit is at fault and the reason your trailer wiring stopped working. You can test it pretty easily with a circuit tester like part # PTW2993 by testing for voltage on the input side of the box when the taillight circuits are applied and then testing the output side as well. If voltage is making it to the box but then not to the other side the issue is internal of the converter and it would need to be replaced.
    view full answer...
  • Difference Between Wiring Harnesses for 2019 Mazda CX-5
    Between the two wiring harnesses that fit your 2019 Mazda CX-5, Tekonsha # 118746 and Curt # C56377, I recommend the Tekonsha. It has a higher maximum amperage than the Curt. Another reason I recommend the Tekonsha is simply because we've always had better success with their reliability. I also prefer how the Tekonsha's converter box actually uses a screw to anchor it in place where the Curt's is just doublesided tape.
    view full answer...
  • Hidden Trailer Hitch Recommendation for 2020 Mazda CX-5
    For your 2020 Mazda CX-5 the hitch I recommend is the Curt # C13315 as it's a 2 inch hitch that's mostly hidden due to the hitch opening being the only portion of the hitch that's visible. I attached a picture that shows what it looks like as well as a link to an install video for you to check out as well. If you need trailer wiring the Curt kit part # C56377 is a confirmed fit and is very easy to install as well. If you wanted to do some towing you might be interested in etrailer...
    view full answer...
  • Comparing Tekonsha and Curt Trailer Wiring Harnesses for 2019 Mazda CX-5
    Both the Tekonsha T-One Vehicle Wiring Harness # 118746 and the Curt T-Connector # C56377 are designed to fit your 2019 Mazda CX-5, and will install in the same manner by plugging into existing ports behind the trim panels in the vehicle's rear cargo area. Both also require a hot lead to be run up to the battery for power. Between the two options though I do recommend the Tekonsha T-One # 118746 because it features a higher amp capacity for its circuits and also uses a superior converter...
    view full answer...
  • Recommended Trailer Wiring Harness for 2019 Mazda CX-5
    Curt and Tekonsha both offer wiring harnesses for your CX-5. The Tekonsha model is # 118746 and the Curt is # C56377. Both install in the same manner, by plugging inline between the vehicle's taillight assemblies and the wiring harness that feeds them. No cutting or splicing required. Because the Tekonsha # 118746 has a higher amperage rating 5 amps/each stop/turn circuit and 7 amps/each taillight circuit as opposed to 3 amp/6 amps for the Curt model, I'd recommend the Tekonsha. Aside...
    view full answer...
  • Hitch Install Difficulty and Bike Rack Recommendation for 2020 Mazda CX-5
    The install process for the Curt Class III Receiver Hitch part # C13315 is actually pretty simple and you do not need to remove your bumper. The only part that you need to remove is the small plastic trim piece that is on the bottom side of your fascia. Once removed you will not be re-installing it. I have attached a video to this page showing how the hitch installs on a 2018 CX-5 for your reference. It will be the same process for your 2020 since they are the same generation. For a...
    view full answer...
  • Trailer Wiring Comparison for 2017 Mazda CX-5 Tekonsha Compared to Curt
    For your 2017 Mazda CX-5 we have two trailer wiring harnesses available. The Curt part # C56377 and the Tekonsha part # 118746 which you mentioned. In general the Tekonsha kits are more reliable and less likely to short out. Partially due to the fact the Tekonsha has a higher amperage rating: # 118746 Stop/turn lights: 5 amps per circuit Tail lights: 7.5 amps per circuit Compared to # C56377 Stop/turn lights: 3 amps per circuit Tail lights: 6 amps per circuit
    view full answer...
  • Curt Trailer Wiring Harness # 56310 Not Fitting 2016.5 Mazda CX-5
    It is possible that the tail light connectors on your 2016.5 Mazda CX-5 are the same as what is on the 2017 models. If that is the case it would take harness # C56377. Take a look at the connectors for this harness to see if they match up to what is on your vehicle. If not then the only other option is to use a universal wiring harness such as # 119190KIT and splice it into the tail light wiring on the vehicle. You should not have to break any tabs or modify anything to get a T-connector...
    view full answer...
  • Trailer Wiring Comparison for 2019 Mazda CX-5 Curt or Tekonsha
    For your 2019 Mazda CX-5 we have two trailer wiring harnesses...the Tekonsha kit part # 118746 that I recommend and the Curt # C56377 which is also a solid choice, but the Tekonsha is the better route. The reason I recommend the Tekonsha is because it will be more resistant to internal shorts of the converter box due to shorts on the trailer's wiring. This is mainly due to the higher amperage rating of the converter box (7.5/5 amps compared to 6/3 amps of the Curt) and because in general...
    view full answer...
  • Parts Needed to Install 7 Way Connector on 2019 Mazda CX5
    We have exactly what you're looking for. If you don't already have a 4 way on your 2019 Mazda CX-5 you'll need to add that first using the Curt # C56377, which will provide the base functions you'll need to then install a 7 way. Once you've done that you can add your 7 way with the # ETBC7L, which is designed to be used with wireless trailer brake controllers like the Curt Echo Mobile # C51180. I recommend going this direction over a wired brake controller like the Tekonsha Prodigy P3 #...
    view full answer...
  • How to Install a Trailer Wiring Harness on a 2017 Mazda CX-5
    We have not yet had the chance to install a trailer wiring harness on a 2017 Mazda CX-5 so I would not have any additional advice for you outside of what is laid out in the instruction manual. However, I see you purchased the T-One Vehicle Wiring Harness part # 118746 which means you would have received the instructions included with this kit which I agree are rather vague. However, the process to install the trailer wiring harness will be the same as the Curt T-Connector Vehicle Wiring...
    view full answer...
  • Can Wiring Harness be Installed After Hitch on 2017 Mazda CX-5?
    To answer your first question, yes, you would be able to install wiring after you have put in Draw-Tite # 76138. In regards to your second question, the answer is it depends on the harness. For example, Curt T-Connector # C56377 is a confirmed fit for your 2017 Mazda CX-5, and it could be installed without drilling.
    view full answer...
  • Can the Rear Accessory Socket on a 2017 Mazda CX-5 be Used to Power the T-One # 118746
    Although the recent CX-5s may have a power source bus in the hatch area you will want to run the wire for power to the battery. The Tekonsha T-One # 118746 is a new kit for 2017+ Mazda CX-5s which Tekonsha designed specifically for your vehicle. Since both Tekonsha and Curt (for the Kit # C56377) say that you need to route the power wire directly to the battery that is the best route to go. After routing the wire up to the battery you need to install the included fuse and connect it...
    view full answer...
  • Trailer Wiring Recommendation for 2017 Mazda CX-5
    For your 2017 Mazda CX-5 the correct Curt trailer wiring harness is the part # C56377. The other kits you mentioned are not a fit for your vehicle so they would not work. Not all vehicles can handle the additional amperage draw of the trailer taillights on the vehicle taillight circuits. Those vehicles need setup that draws power from the battery. Some vehicles have higher rated circuits that can handle this, and others need to have the power drawn straight from the battery to protect...
    view full answer...
  • Will the Trailer Hitch for a 2016 Mazda CX-5 Fit a 2020 Mazda CX-5
    Yes, the trailer hitch for a 2016 Mazda CX-5 is the same as the trailer hitch for a 2020 Mazda CX-5. That said, the Curt Trailer Hitch Receiver part # C13315 and etrailer Trailer Hitch Receiver part # e98902 are currently (February 2020) the only confirmed fits for a 2019 Mazda CX-5. Furthermore, you can't reuse hardware if you are transferring the hitch from one vehicle to another so you will need the Replacement Hardware Kit for Trailer Hitches part # RHK. If you will be towing a trailer...
    view full answer...
  • If asked to choose between the Tekonsha # 118746 or a Curt # C56377 I'd go with the Tekonsha. The Tekonsha model has a higher amperage rating, and over the years we've found their electrical products to be slightly more reliable in the long run than those from Curt. Curt makes a great product, but the Tekonsha is just a little bit better. If you click the provided link, you can see the harness I recommended being installed on a 2017 CX-5. The procedure on your vehicle would be identical.
    view full answer...

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Info for this part was:

Expert Research:
Mike L
Expert Research:
Jameson C
Edited by:
Lindsey S
Video Edited:
Jacob T
Installed by:
Cole B
Updated by:
Sarah W
Updated by:
Kristina F
Updated by:
Isabelle B
Written by:
Amanda M

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