Stop wrestling with butt connectors and electrical tape. The CURT 56170 is a custom-fit, vehicle-specific trailer wiring harness that connects directly to your tow vehicle's factory tail-light plug -- no cutting, no splicing, no voiding your vehicle warranty. It outputs a standard 4-pin flat connector at the hitch end, giving you running lights, brake lights, and turn signals ready for any flat-4 trailer or RV tow connection.
Generic T-one harnesses work, but a custom-fit unit like the CURT 56170 is engineered for a specific vehicle make and model. The vehicle-side connector matches your factory tail-light socket exactly, so installation is a matter of unplugging the OEM harness, plugging in the CURT unit, and routing the 4-pin flat to the hitch area. Most installs take under 30 minutes and require no tools beyond basic hand tools for routing and securing the cable.
CURT's custom wiring line -- of which the 56170 is a part -- is designed to integrate with the vehicle's existing lighting circuit without overtaxing it. The harness includes an internal circuit protection module on most applications, preventing back-feed from trailer lights that could interfere with modern vehicle electronics or trigger dashboard warning lights.
Plugs directly into the factory tail-light harness connector. No wire cutting or splicing required for a clean, warranty-friendly install.
Industry-standard 4-pin flat trailer connector at the hitch end. Compatible with the vast majority of utility trailers, boat trailers, and tow dollies.
Built-in protection module guards your vehicle's electrical system against shorts or back-feed from trailer lighting -- critical on modern CAN-bus equipped vehicles.
Vehicle-side connectors are molded to OEM specifications for a secure, rattle-free fit at the factory tail-light socket.
The 4-pin flat is the most common trailer wiring standard in North America. The CURT 56170 delivers all four standard circuits through this connector:
Note: The standard 4-pin flat does not carry a 12V auxiliary power circuit or electric brake output. If your trailer requires electric brakes, you will need a 5-pin or 7-pin connector setup instead.
Unlike universal T-one harnesses that require you to splice into your vehicle's wiring loom, the 56170 uses OEM-matched connectors at the vehicle end. This means your factory wiring is untouched, the install is fully reversible, and there is no risk of corrosion at splice points years down the road.
Installation follows the same straightforward process common to all CURT custom-fit harnesses:
No drilling, no soldering, and no wiring diagram expertise required for most applications.
The CURT 56170 is a vehicle-specific part number engineered for a particular make, model, and model year range. Verify your vehicle's year, make, and model against CURT's online fit guide before ordering to confirm this is the correct harness for your application. Using a harness designed for a different vehicle may result in connector mismatch or improper circuit function.
After installation, apply dielectric grease to the 4-pin flat connector before each towing season. This prevents corrosion at the trailer-side contact pins, which is one of the most common causes of intermittent trailer light failures. Inspect the vehicle-side connectors annually for moisture intrusion, and ensure the cable is re-secured if it loosens from body clips over time.
If your trailer or RV uses electric brakes or requires a 12V auxiliary circuit, CURT offers companion 5-pin flat and 7-pin RV-blade custom harnesses for many of the same vehicle applications. Look for CURT's 5-way or 7-way custom-fit harnesses in the same product family for those upgraded requirements.