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Curt 55567 T-One Vehicle Wiring Harness T-Connector for Trailer Towing

CURT 55567 T-One vehicle wiring harness T-connector for trailer towing, plug-and-play 4-flat design, 1.49 lbs, 9x6x3 inches
 
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: $59.19
Part Number: 55567
Manufacturer: Curt MFG

Quantity in Stock :35

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CURT ManufacturingPlug-and-Play -- No Splicing4-Flat ConnectorCURT 55567 T-One T-Connector Trailer Wiring Harness

Add trailer lighting capability to your tow vehicle the right way -- without cutting, splicing, or taping into factory wires. The CURT 55567 T-One connector integrates directly with your vehicle's existing tail light wiring harness, delivering clean, reliable trailer signals in a fraction of the time of traditional wiring jobs. Whether you're towing a pop-up camper, utility trailer, boat trailer, or small travel trailer, this is the starting point for a legal, safe lighting connection.

Plug Into Your Factory Harness -- No Wire Cutting Required

The CURT T-One (T-connector) system is one of the most popular trailer wiring solutions on the market for good reason. The harness is engineered to plug directly into your vehicle's existing tail light sockets or OEM wiring connectors, acting as a pass-through that simultaneously feeds your trailer's turn signals, brake lights, and running lights without disrupting the vehicle's original electrical system.

Part number 55567 is a vehicle-specific fitment within CURT's extensive T-One lineup. Rather than a universal splice-in kit, this connector is shaped and keyed for the exact connectors found on the compatible tow vehicles it serves, ensuring a secure, moisture-resistant fit. The result is a professional-looking install that a dealer could charge significant labor for -- done in your driveway in under an hour.

No-Splice Design

Plugs directly into OEM tail light connectors. Zero wire cutting means no voided warranties and no risk of shorts from improper splicing.

4-Flat Output

Outputs a standard 4-pin flat trailer connector -- the universal standard for most utility, boat, and small travel trailers across North America.

Vehicle-Specific Fit

Engineered as a direct plug-in for compatible vehicle tail light harness connectors. No adapter guesswork, no universal trimming required.

Carries Full Signal Set

Transfers left turn/brake, right turn/brake, running/taillights, and ground -- all four functions required for legal trailer operation in all 50 states.

What the T-One System Does

The T-One sits between your vehicle's tail light bulb socket (or OEM wiring plug) and the original connector, acting as a signal splitter. It reads the same signals your vehicle's taillights use and replicates them on the 4-flat trailer connector pigtail that hangs at the rear of your vehicle, ready to mate with your trailer's 4-flat plug.

  • Left turn and brake signal output
  • Right turn and brake signal output
  • Running light and taillight output
  • Ground wire -- typically requires attachment to a solid chassis ground point
Clean Factory-Look Install: Because the T-One integrates at the socket level, there are no exposed splice points, no heat-shrink bundles, and no tape wads tucked behind your taillight housing. The harness routes cleanly and the 4-flat connector can be stored or mounted near your hitch receiver when not in use.

Compatible Trailer Types

The 4-flat output connector on the CURT 55567 is compatible with the vast majority of trailers used in the recreational and utility markets:

  • Pop-up campers and folding trailers
  • Small to mid-size travel trailers (single axle and tandem, as long as they use 4-flat)
  • Utility trailers and cargo trailers
  • Boat trailers and personal watercraft trailers
  • Motorcycle and ATV trailers
  • Landscape and equipment trailers with 4-flat connectors
4-Flat vs. 5-Flat/7-Pin: The 4-flat connector handles the four basic lighting functions only. It does not carry 12V auxiliary power, electric brake output, or battery charge lines. If your trailer has electric brakes or requires a powered 12V circuit, you will need a 5-flat or 7-pin RV blade harness instead. The CURT 55567 is intended for trailers with surge brakes or no brakes, using lighting only.

Installation Overview

Installation is straightforward and requires no special tools beyond basic hand tools to access the taillight area. General process for most vehicles:

  • Remove taillight assemblies or access panels as needed to reach the OEM wiring connectors
  • Unplug the factory connector feeding each taillight
  • Insert the T-One harness connectors in-line -- one side to the vehicle harness, the other to the original taillight
  • Route the 4-flat pigtail along the frame or bumper to the hitch area
  • Attach the ground wire to a clean, unpainted chassis metal surface
  • Test all functions with trailer connected before driving
Maintenance Tip: Apply dielectric grease to all connector pins at installation and re-apply annually. Road grime, moisture, and salt can corrode the 4-flat connector pins over time, causing intermittent signal failures. A cap or plug on the 4-flat connector when not in use extends its service life significantly.
Ground Connection Matters: A poor ground is the number-one cause of trailer lighting problems. Make sure the ground wire from this harness is attached to bare metal -- not a painted surface, not a plastic bracket. A solid chassis ground ensures stable, flicker-free operation of all lighting functions.
Complete the Towing Setup: Pair this wiring harness with a CURT trailer hitch receiver, ball mount, and hitch ball for a complete towing system. CURT offers matching components across their product lineup to ensure electrical and mechanical compatibility.

Product Specifications

ManufacturerCURT Manufacturing
Part Number55567
UPC612314555673
Product Weight1.49 lbs
Package Dimensions9.0 in x 6.0 in x 3.0 in
Product TypeT-One Vehicle Wiring Harness (T-Connector)
SeriesCURT T-One (T-connector) Series

Connector Specifications

Output Connector Type4-Flat (4-pin flat)
Input ConnectionVehicle-specific plug-in, no splicing
Circuits SupportedLeft turn/brake, right turn/brake, running lights, ground
Electric Brake OutputNot included -- lighting only
Auxiliary 12V OutputNot included

Compatibility and Fitment

Wiring MethodPlug-and-play, vehicle-specific direct plug-in
Trailer Connector StandardStandard 4-flat, compatible with North American trailers
Typical ApplicationsUtility trailers, boat trailers, pop-up campers, small travel trailers
Brake Controller CompatibleNo -- 4-flat does not support electric brake signal

Regulatory and Compliance

Legal UseMeets all 50-state trailer lighting requirements for 4-function trailers
SAE ComplianceSignals comply with SAE standards for turn, brake, and running lights

Package Contents

IncludedT-connector wiring harness with 4-flat pigtail and vehicle-specific plugs
Not IncludedMounting hardware (typically not required), hitch receiver, ball mount, trailer ball
Important Information
  • Verify this part number (55567) is the correct vehicle-specific fit for your year, make, and model before installation. CURT's online vehicle selector or tech support can confirm compatibility.
  • This harness supports 4-flat lighting functions only -- it does NOT support electric trailer brakes, 12V trailer battery charging, or 5-wire/7-pin trailer connectors.
  • Do not exceed the current rating of the harness. Overloading with aftermarket LED light bars or additional circuits not present on the original trailer wiring can damage the connector and vehicle circuits.
  • A proper chassis ground connection is mandatory. Failure to ground correctly will cause lighting malfunctions on one or both sides of the trailer.
  • LED-equipped vehicles may require a CURT custom wiring solution or resistor kit if the T-One triggers a "trailer not connected" or rapid-flash warning on the vehicle's instrument cluster. Check vehicle LED compatibility before purchasing.
  • Not intended for trailers with electric brakes. If your trailer has electric drum or disc brakes, a 7-way RV blade connector and a brake controller are required.


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