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Curt 56226 Custom Fit Trailer Wiring Connector -- Vehicle-Side 4-Pin Flat Harness

CURT 56226 custom fit vehicle-side 4-pin flat trailer wiring connector harness for plug-and-play towing hookup
 
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Part Number: 56226
Manufacturer: Curt MFG

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CURT Manufacturing4-Pin FlatNo-Splice InstallCURT 56226 Custom Fit Trailer Wiring Connector -- Plug-and-Play 4-Pin Flat Harness

Stop wrestling with wire taps and electrical tape. The CURT 56226 is a vehicle-specific, custom-fit trailer wiring connector designed to plug directly into your vehicle's factory tail light harness -- no splicing, no cutting, no guesswork. You get a clean, reliable 4-pin flat output that powers your trailer's running lights, brake lights, and turn signals exactly as the factory intended.

Clean Towing Wiring Without the Mess

Generic universal wiring kits mean spliced wires, heat-shrink joints buried behind trim panels, and the constant worry that a bad splice will leave you with no trailer lights on the highway. CURT's custom-fit wiring approach eliminates all of that. The 56226 uses vehicle-specific connectors that match the OEM plugs on your tail light assemblies, so installation is typically a simple unplug-and-reconnect job that takes under an hour.

The harness includes a 4-pin flat connector -- the most universal trailer-side standard in use today -- so it will mate with virtually every standard trailer on the road, from utility trailers to boat trailers to small campers and cargo haulers.

No-Splice Design

Plugs directly into factory tail light connectors. No cutting or splicing into your vehicle's wiring. Preserves factory warranty integrity.

4-Pin Flat Output

Delivers running/tail lights, left turn/brake, right turn/brake, and ground -- the four circuits needed for standard single-axle trailer operation.

Vehicle-Specific Fit

Engineered to match OEM connector locations and pin assignments for the target vehicle, eliminating adapter hassles and wiring reversals.

T-One Connector Style

Draws power from both sides of the vehicle's tail light circuit and uses an integrated circuit board to isolate trailer load from vehicle electronics.

Why Custom Fit Matters on Modern Vehicles

Late-model trucks and SUVs use multiplex or CAN-bus controlled lighting systems. Splicing directly into these circuits can trigger fault codes, blow fuses in the body control module, or cause flickering. CURT's T-One style connectors include a built-in converter/isolator that reads the factory signal without loading the circuit, keeping your BCM happy and your trailer lights steady.

What This Harness Powers

The 4-pin flat connector on the trailer end carries these four circuits:

  • Pin 1 -- Ground (White): Common ground return for all trailer lighting
  • Pin 2 -- Left Turn and Brake (Yellow): Left trailer lamp signal
  • Pin 3 -- Tail/Running Lights (Brown): Trailer marker and running lamps
  • Pin 4 -- Right Turn and Brake (Green): Right trailer lamp signal

This is the SAE J1239 standard 4-flat pinout, compatible with the vast majority of trailers sold in North America. If your trailer requires more circuits (12V auxiliary, electric brakes), you will need a 5-pin or 7-pin solution instead -- the 56226 is a 4-circuit harness only.

Part of CURT's T-One Connector Family

CURT manufactures vehicle-specific T-One connectors for hundreds of makes and models. The 56226 is one part in that lineup, engineered for a particular vehicle application. Always verify your vehicle's year, make, model, and trim before ordering to confirm this is the correct connector for your application. CURT's online vehicle fitment guide cross-references part numbers to specific vehicle configurations.

Installation Overview

Typical installation for a CURT T-One style connector:

  • Open the vehicle's tail light access panel or remove the tail light assembly (usually 2-4 screws)
  • Unplug the factory connector from the tail light
  • Plug the T-One harness in-line between the factory connector and the tail light
  • Route the 4-pin flat pigtail to the rear hitch area
  • Secure the harness with the included zip ties to prevent chafing
  • Plug in a test trailer or 4-pin tester and verify all circuits

No drilling, no crimping tools, and no electrical tape required for most applications. Total install time is typically 20 to 45 minutes.

Maintenance Tips
  • Apply dielectric grease to the 4-pin flat connector before each towing season to prevent corrosion
  • Store the unused connector end with a dust cap when not towing
  • If trailer lights flicker, check the ground pin first -- a loose ground is the most common cause
  • Inspect the in-line harness annually for chafing near hitch receiver edges
Not for Electric Brake or 12V Auxiliary Circuits

The 56226 provides four circuits only (ground, tail, left turn/brake, right turn/brake). It does not support electric trailer brakes, a 12V battery charge line, or reverse lights. If your trailer or camper requires any of these functions, you need a 5-pin flat or 7-pin round connector system instead.

Product Specifications

ManufacturerCURT Manufacturing
Part Number56226
UPC612314562268
Connector TypeCustom Fit T-One (vehicle-side plug-in)
Output Connector4-Pin Flat (SAE J1239)
Installation MethodNo-splice, plug-in to factory tail light harness
Weight1.33 lbs
Package Dimensions11.0 in x 9.0 in x 3.0 in

Electrical Circuits

Circuit 1Ground (White wire)
Circuit 2Left Turn and Brake (Yellow wire)
Circuit 3Tail / Running Lights (Brown wire)
Circuit 4Right Turn and Brake (Green wire)
Electric BrakesNot supported
12V AuxiliaryNot supported

Compatibility and Fitment

Fitment TypeVehicle-specific -- verify year/make/model before ordering
Trailer Connector Standard4-Pin Flat -- fits the majority of standard utility, boat, and cargo trailers
Wiring SystemCompatible with conventional and select multiplexed factory tail light systems

Package Contents

IncludedCustom-fit T-One wiring harness with 4-pin flat pigtail, mounting hardware, zip ties
Not IncludedTrailer connector dust cap (recommended, sold separately), brake controller wiring

Certifications and Standards

Connector StandardSAE J1239 4-Pin Flat
CURT Product LineCustom Fit / T-One Connector Series
Important Information -- Read Before Ordering
  • This is a vehicle-specific connector. You must confirm your vehicle's exact year, make, model, and trim match the fitment application for CURT part 56226 before purchase. Installing on an incompatible vehicle can result in non-function or electrical faults.
  • This harness supports 4 circuits only. It does not support electric trailer brakes. If your trailer has electric brakes, a brake controller and 7-pin wiring system are required.
  • Do not exceed the current capacity of the vehicle's factory tail light circuit. The T-One design shares the factory circuit -- adding high-draw LED replacement bars on the trailer without a converter module can cause issues.
  • On vehicles with LED factory tail lights, verify the harness includes or is compatible with a load resistor or converter to prevent hyper-flashing.
  • Always test all four circuits with a plug-in tester or test trailer before your first trip after installation.


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