Trailer Wiring Diagram and Installation Help - Towing 101 (2024)

Any vehicle towing a trailer requires a trailer wiring harness to safely connect the taillights, turn signals, brake lights and other necessary electrical systems.

If your vehicle is not equipped with working trailer wiring, there are a number of different solutions to provide the perfect fit for your specific vehicle. Complete with a color coded trailer wiring diagram of each plug type, this guide walks through each available solution, including custom wiring, splice-in wiring and replacement wiring.

If you're looking to replace the wiring on your trailer, check out ourtrailer rewiring guide.

A. Custom wiring

Vehicle-specific plug-and-play harness that requires no splicing and provides a standard trailer connector

B. Splice-in wiring

Taillight converter that splices into your existing vehicle wiring and provides a standard trailer connector

C. Replacement plugs and sockets

Trailer plugs and vehicle sockets to splice in and replace damaged wiring connectors

Custom wiring is the ideal solution for installing trailer light wiring on your vehicle. A custom wiring harness or 'T-connector' is a vehicle-specific harness that plugs in without any spicing required and provides a standard connector output, such as a 4-way flat.

All CURT custom wiring comes with the exact components needed for a complete installation on the vehicle, including vehicle-specific plugs and an electrical converter, if needed.

Another type of custom wiring is original-equipment (OE) wiring or USCAR wiring. Select vehicles come with a standardized USCAR socket that provides a connection point for a CURT OE wiring harness.

Like a T-connector, anoriginal equipment wiring harnessplugs into the USCAR socket without any cutting, splicing or soldering required, and it provides a standard trailer wiring output, such as a 4-way flat or 7-way RV blade.

Learn more about USCAR wiring

If custom wiring is not available for your particular make and model, a taillight converter may be required to equip your vehicle with the proper trailer light wiring connection.

A taillight converter or electrical converter splices into your vehicle and provides a standard trailer plug wiring connector, typically a 4-way flat. The converter converts the vehicle's complex wiring system to be compatible with your trailer's simple wiring system. To learn more about vehicle wiring systems, check out ourvehicle wiring systems guide.

If the trailer plug wiring on your vehicle or trailer is damaged or not working correctly, you can replace the connector with a CURT splice-in plug or socket.

Plugs (trailer side) and sockets (vehicle side) are available in all standard formats and can be spliced into your existing trailer plug wiring. Find the trailer light wiring diagram below that corresponds to your existing configuration.

If you are rewiring your trailer completely, check out ourtrailer rewiring guide.

Following the standard method for wiring a trailer connector is vital to the safety of your vehicle while towing. Connecting the wrong color wires will result in mismatched taillight functions and confusion on the road.

Use this 4-pin wiring diagram to properly wire your 4-wire trailer plug.

5-pin trailer wiring is very similar to 4-pin wiring, but it adds in a blue wire for the reverse or backup lights.

Not all trailers have reverse lights, so consider your own trailer as you wire in a 5-way plug.

6-pin trailer wiring introduces two new functions, a wire for connecting trailer brakes and a wire for +12-volt auxiliary power.

6-way wiring is most common on gooseneck trailers and allows for use with a brake controller.

The 7-way round trailer plug is to be distinguished from 7-way RV blade plugs. The wiring connections and placement are different.

Be sure to review your own trailer connector before wiring.

The SAE configuration of a 7-way RV blade plug should not be confused with the traditional configuration. Different wire colors are used for different functions.

Review your own trailer before wiring.

7-pin trailer wiring is one of the most popular wiring configruations, particularly the traditional configuration versus the SAE J2863.

Use this 7-pin trailer wiring diagram to properly wire your 7-pin trailer plug.