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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 # C55378
Retail:$91.03
Our Price: $56.14
You Save: 38%
Custom Fit Vehicle Wiring

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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 C55378 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 (76)
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CURT Custom Fit Vehicle Wiring - C55378

  • 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.


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 - no cutting or splicing of wires
    • Locate connection point behind rear bumper
    • Plug in connector
    • Plug in fuse holder under hood
  • 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 behind the rear bumper, along the driver's-side frame rail. Once you've plugged in the T-connector, locate the truck's power wire on the driver's side of the engine compartment and plug the included fuse holder into the matching connector on the power wire. Then attach the fuse holder to the positive terminal on the truck's battery.


Once installation is complete, the 4-way connector will be stowed beneath your vehicle, near the trailer hitch. A mounting bracket (sold separately) is recommended to keep the connector secure.


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.



55378 CURT T-Connector - Surface Mount Technology - 4 Wire

Installation Details C55378 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 - C55378

Average Customer Rating:  4.9 out of 5 stars   (76 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.

by:

So far the device seems to be working as expected. It is easy to install, as it simply plugs into my truck's existing wiring harness. I recall that I mounted it using zip ties, which takes a little bit of time to do properly. I have often found that these Flat 4 adaptors fail internally after a few years...I hope that this one lasts a bit longer.
Coincidentally, the flat 4 to 7-way adapter that I installed after THIS wiring harness, seems to have lost signal to one of the turn signal lights, but this is another issue to do with another piece of equipment. Where I live and drive in Western Canada, the salt on the roads in winter often plays havoc on the undercarriage of vehicles, including any exposed electrical connections. As the song goes, "Oh what fun it is to ride...."!



by:

I haven't installed yet, but etrailer is a great company. Excellent selection of accessories and knowledgeable technical support.



by:

I got late but was very pleased to find out it worked exactly as y’all said it would. Easy to install too. I’m very happy. Thank you.

Kevin

4/22/2024

I’ve use this product for a year now and it’s great. Gave me no problem or issues. I’m very pleased with this product.



by:
2002 Toyota Tundra

Product installed very easily by following the simple instructions. Nicely done, thank you.



by:

Effortless through the entire transacti on!



by:
2002 Toyota Tundra

Excellent in every way.



by:

The product itself is very good - no complaints. The installation instructions don't really match the product (for example, the instructions say that the rear end of the tow harness is on the passenger side; but the picture on the instructions, the video, and my truck(!) all agree that it's on the driver's side). The video was quite accurate, so I suggest you follow the video.



by:
2015 Toyota Tundra

The wire harness for my trailer went out on my 2001 Tundra. After checking with local businesses, I discovered that it would cost about 150 dollars to get a harness installed. I decided to check the internet and found a video produced by etrailer. The video showed how easy it is to do the installation yourself. I ordered the harness that fits my truck, and the delivery was fast. Taking my time, I installed the harness in about 15 minutes and saved 100 dollars in labor. By the way, the new harness works as it should. I have purchased several products from etrailer and was pleased with every purchase.

John H.

10/22/2018

It has been one year since purchasing this wire harness. Am still very pleased. The harness works with zero problems.



by:

The harness worked great and the video as to where the connector was under the vehicle was, as it wasn't where you would expect, was very helpful. Thanks!

Lyle

4/19/2022

No issues with the connector after a year. Great product and help!



by:

You have to have this to run your trailer lights. I wired my initially by tapping into the wires going to the brake lights. Everything was fine until I plugged in the trailer wire harness. Didnt know you needed to come straight off the battery either. This harness solved all those issues. Very happy I bought this.



by:

Awesome service and fast delivery



by:
2002 Toyota Tundra

Making electrical connections on a car, truck or other vehicle can, at times, be a challenge. The C55378 wiring kit for my 2002 Tundra was a breeze to install. The instructions are very clear and the video on the eTrailer web site made installation that much easier. Not sure about the converter electronics but the turn signal draw on the blinker controller didn't make the blinker indicator operate at warp speed and burn the controller out! All the necessary cable ties and adhesive pad are included in the kit; nothing else to buy or add; other than your trailer!

Once again, the folks at eTrailer are great communicators and kept me advised of the product whereabouts through the entire order process.



by:
2001 Toyota Tundra

Super happy with service and product quality of the trailer wiring harness adapter I ordered. Straight forward and simple 10 min installation. The instructions were a little off as far as location of factory harness to plug into, but that's not a difficult thing to figure out on your own. Will use etrailer whenever they have what I need.



by:
2002 Toyota Tundra

I received the wiring adapter very quickly after I placed my order. I had already watched the video etrailer.com, that was specific to my 2002 Toyota Tundra, so the install was straight forward and simple. My truck had a 4 pin connector spliced in by the previous owner but the brake lights didn’t work on my trailer. I installed the adapter kit and everything works as it should now. I’m super impressed with the products, the communication, and the info provided by etrailer. Etrailer.com is top notch, thank you!



by:
2002 Toyota Tundra

This wiring kit was a great solution to my problem. I had old, corroded wring at the end of my 4-pole trailer connector. I found the etrailer videos very helpful in pointing me to how easy it can be to replace just the corroded peice. The parts were just the right parts, fit perfectly and took about 20-min to get the whole thing done. And the shipping at the normal rate was fast...ordered on a Sat PM and received on Tues.



by:

works ok , but need a reminder to double check plug ins before closing up ones work as the new pins will push backwards and not connect then after one closes up he will find a light not blinking properly , did go back and take car apart and find the pins that didnt connect properly , then all worked , thanks , david



by:
2002 Toyota Tundra

My 2002 Tundra had the factory tow package but the converter (behind left tailight) was bad. Only my left turn signal and left brake light worked on trailer. This product plugged into factory harness easily and fixed my problem.



by:
2001 Toyota Tundra

Fast shipping and easy installation. Thanks etrailer.

Michael V.

6/9/2019

No problems whatsoever. Still works like new.



by:

Purchasing from etrailer.com was an excellent experience! The wiring harness arrived promptly, and it was a quick installation. It was an immediate fix of the trailer lighting on my vehicle. I will definitely go back to etrailer when the products they carry are needed.
A very pleased customer, Sid Strickland



by:
2002 Toyota Tundra

Unlike other online dealers etrailer.com has a very well designed web site that is easy to navigate. What was really helpfully were the utube instructional videos. They made a Video for installation of the trailer wire harness for my 2002 Toyota Tundra. Impressive.



by:
Toyota Tundra

FANTASTIC PRODUCT. I did not realize that my tundra required a control box to make the brake lights work, as I had been struggling with it for months. Your product snapped right in, and I had brake lights within a matter of seconds. Very pleased



by:

I used two Curt connectors on my 2001 Toyota tundra. Both weren't working and I wasn't getting power to the 4 pin. I switched it out for the T one brand and I finally got it to work. Just in time because I was moving out of state with it in the next 6 days.



by:
2002 Toyota Tundra

The curt T-connector was an exact matched fit to my 2002 Tundra. The instruction videos on your web site were very good quality. You are now my go-to connection for trailer parts. Thanks.



by:
2002 Toyota Tundra

Excellent because I just installed it. Had a T-One I bought from ETrailer 10 years ago that finally went bad. ETrailer does an excellent job with selection and service. I chose the Curt model due to highter amps per circuit 9 as compared to 7.5. Towing something with a higher amps draw is the best way to destroy it and never use more than a 10 amp fuse!!!



by:

Very easy installation, Very easy installation, Product works as is supposed to, I am very happy with the product. Would definitely purchase from etrailer.com again.


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

  • Why Are My Trailer Taillights Staying On when Using the Curt Harness # C55378?
    If you have tested the Curt Harness # C55378 with a circuit tester on your 2001 Toyota Tundra, there should not be any signal to the plug when the vehicle has the lights off and there should be power to the lights when the vehicle is turned on. If you tested and there is a signal with the lights off, there is a problem with the vehicle's-side of the connection. To rule out any issues with the vehicle's-side of the wiring, make sure that there are no frayed/pinched wiring and that the ground...
    view full answer...
  • 4-Way Trailer Wiring Harness for a 2002 Toyota Tundra
    Wiring harness # C55246 is not a confirmed fit for your 2002 Toyota Tundra but we do have wiring harnesses that will work. To add a 4-Way you can use # C55378, # 118378, or # HM43375. If it were me, I would go with # 118378 because it is the best value and we hear about fewer problems with the Tekonsha brand. I have linked a video showing an example installation for you.
    view full answer...
  • Does Curt Trailer Wiring Harness for 2001 Toyota Tundra Have Fuse
    The only fuse of the Curt trailer wiring kit part # C55738 is in the red fuse holder you referenced. Most likely if your fuse is good but it's still not working the problem is the converter box. You can test this with a circuit tester like # PTW2993. If there is voltage on the input side of the box when taillight circuits are applied but none on output side the converter box is fried and is in need of replacing the entire kit since they are not available separately.
    view full answer...
  • Parts Needed to Install 7-Way and Brake Controller in 2002 Toyota Tundra
    We can definitely help with a 7-way and brake controller for your 2002 Toyota Tundra but your vehicle was not pre-wired for a brake controller install so the install would be a little more involved. You will need to start with a 4-way (if you do not have one). For that you would want the # C55378. From there you would need to convert the 4-way to a 7-way so that you can install the brake controller. For that you will want the Brake Controller Install Kit and 7-Way Adapter part # ETBC7....
    view full answer...
  • Low Voltage From Converter 4-Way With Curt Harness on 2001 Toyota Tundra
    If you checked the wires right before the converter box of the Curt T-Connector Vehicle Wiring Harness # C55378 for your 2001 Toyota Tundra and got 12 volts, but then tested the wires coming out of the converter and got almost nothing, the issue will be a bad converter, which is rare but happens on occasion. I also do highly recommend going with a Tekonsha wiring harness for your 2001 Tundra, as they make the most reliable harnesses. The correct part for a 2001 Tundra is the Tekonsha T-One...
    view full answer...
  • Recommended 4-Way Wiring Harness for a 2002 Toyota Tundra
    Since your 2002 Toyota Tundra does not have the factory towing package you will need to install the Curt T-Connector Vehicle Wiring Harness item # C55378. This custom-fit T-connector plugs into your Tundra's existing wiring harness behind the rear bumper. It will be on the driver's side frame rail. It will provide you with a 4-way connector to control your trailer's lights. We had a 2002 Tundra in the shop awhile back and I have included an installation video below of the Curt item #...
    view full answer...
  • Troubleshooting Installation of Curt 4-Pole Wiring Harness C55378 in 2002 Toyota Tundra
    The two wiring harness kits you referenced, Curt # C55378 and Tekonsha # 118378, are both correct fits for your 2002 Toyota Tundra. Both of these kits are multi-part harnesses that include the required fuse/fuse holder and the installation of the Curt kit in a 2002 Tundra is shown in the linked video. The troubleshooting steps I suggest are to double-check that all connectors have no bent or damaged contacts, that they are fully seated together and that the ring terminal on the harness...
    view full answer...
    Image 1 for
  • Parts Needed to Add 7-Way to 2002 Toyota Tundra
    In order to get a working 7-way on your 2002 Toyota Tundra to connect to a trailer with a 7-way you will need to add a couple of parts. The first of this is a 4-way in order to get the turn signals and tail light signals, with the easiest install for your truck being the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C55378. Then, to get a 7-way which will allow you to have working connections for a brake controller, 12 volt power, and reverse lights you will...
    view full answer...
  • Does Curt Trailer Wiring Harness C55367 Fit 2001 Toyota Tundra
    For your 2001 Toyota Tundra the correct Curt trailer wiring harness is the part # C55378 which is a confirmed fit. The part # C55367 only fits 2000 Tundras.
    view full answer...
  • Do You Carry a Plug and Play 7-Way For a 2001 Toyota Tundra?
    Currently we only carry a 4-Way # C55378 which is designed to plug into the factory harness on your 2001 Toyota Tundra. For a 7-way you would either need to acquire the factory wiring or use the 4-way with our 7-Way Upgrade # ETBC7 which will provide you with additional wiring for the charge line and brake controller.
    view full answer...
  • Does Curt T-Connector Vehicle Wiring Harness # C55378 work with LED lights
    Yes, the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C55378 that you referenced would work well with LED lights on your vehicle or trailer lights. I attached an install video for this wiring harness for you to check out also.
    view full answer...
  • Is the Curt Converter Box for a 2002 Toyota Tundra Replaceable
    The converter box for the Curt T-Connector Vehicle Wiring Harness part # C55378 is not available as a separate replacement part unfortunately. However, I actually recommend you take a look at the T-One Vehicle Wiring Harness part # 118378 instead which we have found to be much more reliable. The issue that causes the converter boxes to fail is excessive movement. The above Curt converter box attaches using adhesive which is not always the best method. The Tekonsha converter box attaches...
    view full answer...

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


Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Shane T
Test Fit:
Shane T
Employee Leah B
Edited by:
Leah B
Employee Zack K
Video by:
Zack K
Employee Alan C
Video by:
Alan C
Employee Lindsey S
Written by:
Lindsey S
Employee Jeff D
Video Edited:
Jeff D
Employee Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video Edited:
Dustin K
Employee Jameson C
Expert Research:
Jameson C
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B
Employee Noah M
Updated by:
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