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CURT

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

Part Number: C55378

102 Reviews | 15 Questions

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$63.69

Retail:$100.95

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2023 Chrysler Pacifica

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Product Images

curt custom fit vehicle wiring end connector plug-in c55378

curt custom fit vehicle wiring trailer hitch end connector t-connector harness with 4-pole flat

curt custom fit vehicle wiring trailer hitch plug-in t-connector harness with 4-pole flat connector

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In Use/Installed

2001 toyota tundra custom fit vehicle wiring curt trailer hitch 4 flat c55378

2001 toyota tundra custom fit vehicle wiring curt trailer hitch 4 flat t-connector harness with 4-pole connector

2001 toyota tundra custom fit vehicle wiring curt 4 flat plug-in c55378

2001 toyota tundra custom fit vehicle wiring curt end connector plug-in c55378

2001 toyota tundra custom fit vehicle wiring curt end connector 4 flat c55378

2001 toyota tundra custom fit vehicle wiring curt trailer hitch plug-in on a

2001 toyota tundra custom fit vehicle wiring curt end connector 4 flat on a

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Videos

Trailer Wiring Harness Installation - 2001 Toyota Tundra

Review of Curt Custom Fit Vehicle Wiring - Trailer Hitch Wiring - C55378

Trailer Wiring Harness Installation - 2002 Toyota Tundra

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SCHEDULE AN INSTALLATION

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 (102)
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CURT Custom Fit Vehicle Wiring - C55378

Highlights

Custom Fit for Your Vehicle: Works with your vehicle's wiring
Tow Without Factory Prep: 4-way connector powers trailer brake, turn, and tail lights.
Plug-and-Play Install: T-connector plugs into factory harness—no cutting or splicing needed.
Reliable Signal Match: Powered converter keeps vehicle and trailer lighting in sync.
LED-Ready Setup: Works with vehicles or trailers that use LED lights.
7-Way Upgrade Option: Pairs with kit #ETBC7 to add brake controller and 12V charge line.

Features to know about

Installs Fast Without Cutting or Splicing: Plug-In T-Connector

Wiring a trailer doesn’t have to mean chasing wires or cutting into factory circuits. The Curt T-Connector plugs right into the existing vehicle wiring to give you a 4-pole flat connector for trailer lights. Everything connects cleanly behind the rear bumper, so you don’t have to modify any of the factory wiring to get running lights, turn signals, and brake lights working properly.

Protects Vehicle Circuits: Powered Converter Box

This harness includes a powered converter that draws power directly from the battery instead of the vehicle’s lighting system. That keeps sensitive electronics safe from overload or shorts while delivering steady power to the trailer lights. The converter box has an inline fuse for circuit protection and reliable performance over time.

Handles Modern Trailer Lighting: Works with LED Lights

Many newer trailers use LED lighting that can trip up older wiring kits. This harness is built to handle LED loads properly, so your trailer lights will operate as expected with no flicker or compatibility issues. Whether you’re towing a small utility trailer or something larger with low-draw LED lamps, this setup keeps all your signals clear and consistent.

Ready for Future Upgrades: Base for 7-Way Conversion

If you ever need to pull a trailer with electric brakes or an onboard battery, this 4-way is an easy starting point. Just add the 7-Way Upgrade Kit # ETBC7 when you’re ready, and you’ll have what you need for a full brake controller and charge line setup without rewiring everything from scratch.

Specs

Image Description: Comparison image of Curt T-Connector Vehicle Wiring Harness models showing plug types and wiring configurations with labeled callouts for technical reference.

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

Similar to Tekonsha 118378

Installation Details C55378 Installation instructions

This Product Fits The Following Vehicles

2001 - 2002 Toyota Tundra
2000 - 2002 Toyota Tundra excluding factory towable bumper
2001 - 2002 Toyota Tundra including factory towable bumper

Customer Satisfaction Score:

94% were satisfied with this product

6% of customers were not satisfied

Product did not meet expectations
Wrong item was ordered
etrailer mistake

6% of customers were not satisfied

Product did not meet expectations
Wrong item was ordered
etrailer mistake

4.9

102 reviews

5 Stars		(95)
4 Stars		(4)
3 Stars		(1)
2 Stars		(1)
1 Star		(1)

by: Mark 07/30/2025

Did exactly what it was supposed to do! Thank you very much!

Click to Enlarge

Mark One Year Later

7/31/2026

Works fine, no complaints!

by: Scott 07/08/2024

2002 Toyota Tundra

The wrong product, despite being labeled guaranteed to fit. Does not fit the plug on my truck, please help me find the correct wiring harness. 2002 Toyota Tundra. Without proper pics of the plug on the product, I can’t tell what fits! See attached pictures please, my truck plug is on the left. The one I was sent is on the right.

Click to Enlarge

Brooke M.

7/29/2024

Hey Scott! Take heart, we have seen this before! I dont have the ability to post a picture here in the comment but if you go to the link I attached, you will find an expert answer that has a picture of two plugs right next to each other. I am thinking you pulled the wrong one by mistake but the correct one should be right by the on you found. If not, please let me know and we can get you set up with a universal wiring harness that you can splice in like part # HM48240 if need be.

Helpful Links

question-396732.html

Scott One Year Later

7/29/2024

Got help from etrailer. I was trying to use the wrong plug. Found the right one and this product works perfectly! Thanks for the followup etrailer. Can I update my 1-star review since this was operator error?

by: Roderick 06/09/2026

I was told it was gonna fit my Toyota tundra 2000 but it doesn’t

by: Thomas 08/15/2026

Bought the kit, watch the video that was specific to my truck and bam done in minutes with out having to cut or splice.

by: Phil 07/19/2026

2001 Toyota Tundra

It arrived intact and on time, but I thought I also ordered the round plug for heavier use vehicles.

by: Travis 10/31/2025 One Year Later

Easy install! Haven’t had any issues with the harness. I’ve had it for about a year now.

by: John h 10/21/2017

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. One Year Later

10/22/2018

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

by: Eric 01/30/2024 One Year Later

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: Richard 08/16/2021 One Year Later

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: Robin 08/12/2025 One Year Later

Packaged well. Good solid quality, It was pretty easy to install. never done this so I read the directions and figured out what to bypass on my old connection that didn't work and I did it!
It worked out great! I appreciate a company that makes it simple for the do it yourselfer. have used the plug a lot this past year hauling.
Thank you,
Robin

by: Lyle 04/18/2021 One Year Later

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 One Year Later

4/19/2022

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

by: John P 07/14/2018

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: Michael 06/09/2018

2001 Toyota Tundra

Fast shipping and easy installation. Thanks etrailer.

Michael V. One Year Later

6/9/2019

No problems whatsoever. Still works like new.

by: Carson 06/01/2018

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: Bruce 08/05/2014

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: Arnold 11/04/2025

2002 Toyota Tundra

Really good and easy to install. work for toyota tundra 2002

by: Mike M. 08/20/2018

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: Christopher 11/19/2022

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: Marc 09/08/2021

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: Don 11/04/2025

Plug and play
Worked perfectly

by: Kasheef 09/16/2020

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: Andrew B. 08/06/2016

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: david 04/03/2019 One Year Later

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: Adam 06/17/2020

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: Tom H. 02/12/2016

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.

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

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

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...
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Troubleshooting Curt Trailer Wiring Kit for 2001 that Won't Power On
Hey John, yes the black wire pin on your 2001 Toyota Tundra should have 12 volt power on the Curt 4-way trailer wiring kit part # C55378 as this is what provides power for all of the trailer wiring circuits. If it's not active and you've checked all fuses and relays related to it then there's got to be some wiring issue on the truck for that circuit which will be challenging to track down. I would just run a wire from the battery directly and splice it in for the black wire and bypass all...
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Recommended Brake Controller and 7-Way Connector for a 2002 Toyota Tundra
Hey Kaleb I have all the parts you will need to add a 7-Way connector and a brake controller to your 2002 Toyota Tundra but only one of them is going to be plug and play. Everything else will have to be wired in. There is no brake controller adapter for a 2002 Tundra. To add a 7-Way connector to your truck you'll also need to install a 4-way connector because there isn't just one part that'll do the job. Good news is the 4-way connector is plug and play. I have listed what you will need...
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2001 Toyota Tundra - Installed Curt C55378 And No Power To Harness Or To OEM Harness
Hello Robin, thanks for reaching out. It sounds to me like there is an underlying issue with the factory wiring on your truck. The first thing to do will be to open up the fuse box and make sure you don't have any blown fuses. A blown fuse would definitely explain why you are getting no power to any of the trailer wiring harness. If all of the fuses are ok I suspect the wiring on your truck may be damaged or you possibly have a short somewhere. Usually, this kind of issue is best diagnosed...
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...
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....
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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.
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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...
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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...
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...
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.
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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.
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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...
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.
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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...

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Info for this part was:

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