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Curt 56027 T-Connector Vehicle Wiring Harness - 4-Pin Flat Trailer Connector

CURT 56027 T-connector 4-pin flat trailer wiring harness for vehicles, plug-and-play no-splice design, 9 x 4 x 2 inch packaged size
 
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: $28.95
Part Number: 56027
Manufacturer: Curt MFG

Quantity in Stock :33

Availability: In Stock
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CURT Manufacturing4-Pin FlatNo-Splice InstallCURT 56027 T-Connector Trailer Wiring Harness -- Plug-and-Play 4-Pin Flat

Stop wrestling with splicers and tape. The CURT 56027 T-connector plugs directly into your vehicle's existing tail light wiring harness, passing through your factory signals untouched while adding a standard 4-pin flat output for your trailer. It takes about 15 minutes with basic hand tools and leaves your truck or SUV wiring completely reversible.

Clean Trailer Wiring Without Cutting a Single Wire

CURT's T-connector design is built around a simple principle: your vehicle already knows when to signal left, right, and brake -- this harness just taps into that information and passes it to your trailer without interrupting or modifying the factory circuit. The 56027 is a vehicle-specific fit unit engineered for select cars, trucks, and SUVs that use a compatible tail light connector configuration, making it a genuine plug-and-play install rather than a universal splice job.

The harness ships ready to install. Connect one end to your vehicle's tail light harness, run the 4-pin flat pigtail to your hitch receiver area, and you're done. No dielectric splicing, no wire taps, no risk of a short-circuit from a sloppy aftermarket connection.

No-Splice Design

Plugs directly into the factory tail light connector on each side. Factory plug passes through -- no wires cut, no tape, fully reversible.

4-Pin Flat Output

Industry-standard 4-pin flat trailer connector carries left turn/brake, right turn/brake, tail/running lights, and ground. Compatible with the vast majority of small trailers, utility trailers, and boat trailers.

Vehicle-Specific Fit

Molded connectors match OEM tail light harness plugs on compatible vehicles -- no adapter rings, no forcing. Clean fit every time.

Lightweight and Compact

At 0.54 lbs and packaged at 9 x 4 x 2 inches, the harness tucks neatly behind the bumper or along the frame rail without bulky hardware.

What the 56027 Carries -- Wire Function Breakdown

The 4-pin flat connector on this harness handles the four circuits required by most single-axle trailers and all DOT-required lighting functions for trailers under a certain gross weight:

  • Pin 1 (White): Ground -- common chassis ground shared between vehicle and trailer
  • Pin 2 (Brown): Tail/running lights -- energized whenever headlights or parking lights are on
  • Pin 3 (Yellow): Left turn and brake signal
  • Pin 4 (Green): Right turn and brake signal

This is the standard SAE 4-pin flat configuration used across CURT's wiring lineup and recognized by every trailer manufacturer building single-axle utility, landscape, boat, and cargo trailers.

Fully Reversible Install: Because the 56027 uses pass-through connectors rather than splices, you can unplug it completely and return the vehicle to its factory state in minutes. No evidence of modification, no damaged insulation.

What Trailers Can I Tow With This Harness?

The 4-pin flat output covers all lighting circuits required for trailers that do not have electric brakes or 12V auxiliary power needs. That includes:

  • Utility and landscape trailers
  • Boat trailers (single and tandem axle without brakes)
  • Cargo and enclosed trailers without electric brakes
  • Motorcycle and ATV trailers
  • Folding camping trailers with basic lighting only
  • Small pop-up campers without electric brake controllers
Need Brakes or 12V Power? If your trailer has electric brakes or a 12V breakaway battery, you will need a 5-pin or 7-pin connector harness instead. The 56027 is a 4-pin unit and does not carry a brake controller signal or auxiliary 12V feed.

Installation Overview

Most installs follow this sequence -- no vehicle-specific expertise required:

  • Remove the tail light assemblies or access panels on both sides of the vehicle (typically 2-3 screws per side)
  • Unplug the factory tail light connectors
  • Insert the T-connector in-line -- one side to the vehicle harness, one side to the tail light assembly
  • Route the 4-pin flat pigtail along the frame or bumper to the hitch area
  • Secure with zip ties or existing factory clips
  • Reinstall tail light assemblies

Typical install time is 15 to 30 minutes for a first-timer with basic hand tools. No soldering, no test light probing, no wiring diagram required.

Maintenance Tip: Apply dielectric grease to the 4-pin flat connector before first use and whenever you notice corrosion or intermittent signal issues. This is especially important if the pigtail is exposed to road spray or sits unused through the winter. Dielectric grease prevents moisture intrusion without affecting conductivity.
Verify Your Vehicle Fitment Before Ordering: The 56027 is designed for specific vehicle applications. CURT publishes a vehicle fitment lookup by year, make, and model. Confirm your vehicle's tail light connector type matches the 56027 application list. Installing a connector with the wrong keying will not damage your vehicle wiring but it will not seat properly either.
Pair With CURT Trailer Connectors: For the trailer-side connection, CURT's standard 4-pin flat plugs (part 57000 series) and locking flat connectors are a direct match. If you're building out a new trailer harness, staying within the CURT ecosystem ensures connector compatibility.

Package Specifications

ManufacturerCURT Manufacturing
Part Number56027
UPC612314560271
Package Weight0.54 lbs
Package Dimensions9.0 x 4.0 x 2.0 inches

Connector Specifications

Connector TypeT-connector (in-line, no-splice)
Output Connector4-pin flat trailer connector
Number of Circuits4 (ground, tail, left turn/brake, right turn/brake)
Connector KeyingVehicle-specific OEM-match plugs
Installation MethodPlug-and-play, no splicing required

Compatibility

Trailer Types SupportedUtility, boat, cargo, motorcycle, ATV, pop-up camper (non-brake)
Electric Brake SupportNo -- 4-pin flat does not carry brake controller signal
Auxiliary 12V SupportNo -- upgrade to 5-pin or 7-pin for 12V feed
Vehicle FitmentSelect cars, trucks, and SUVs -- verify by year/make/model

Wiring Pin Reference

White Wire / PinGround
Brown Wire / PinTail / Running Lights
Yellow Wire / PinLeft Turn and Brake
Green Wire / PinRight Turn and Brake

What Is Included

IncludedT-connector wiring harness with 4-pin flat pigtail
Not IncludedMounting hardware, zip ties, dielectric grease, trailer-side connector
Important Information
  • The 56027 is a 4-pin flat harness only -- it does not support electric trailer brakes. If your trailer has electric brakes, you need a 7-pin connector and a separate brake controller wiring harness.
  • Always verify vehicle fitment using CURT's year/make/model lookup before installation. Connector keying is vehicle-specific and this harness will not seat correctly on non-compatible vehicles.
  • Do not exceed the current rating of your vehicle's tail light circuit. The T-connector passes factory signals through -- overloading with excessive trailer lighting can blow a factory fuse.
  • If trailer turn signals flash rapidly (hyper-flash) after install, your vehicle may have LED tail lights that require a load resistor or LED-compatible harness variant. Check CURT's fitment guide for an LED-optimized alternative if this applies.
  • Keep the 4-pin flat pigtail capped with its dust cover when not in use to prevent pin corrosion from road debris and moisture.


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