4 Pin Wiring Diagram Trailer

Hello and welcome to our article about 4 pin wiring diagram for trailers. In this guide, we will provide you with a detailed explanation of the 4 pin wiring diagram, its advantages and disadvantages, as well as alternative options. So, let’s dive in and explore the world of trailer wiring!

1. Understanding the Basics

Before we start discussing the 4 pin wiring diagram, it’s important to have a basic understanding of trailer wiring. Trailers typically have electrical systems that allow them to operate lights and other accessories while being towed. The wiring system connects the trailer’s lights to the towing vehicle’s electrical system, ensuring proper functioning of the lights and signals.

2. The 4 Pin Wiring Diagram

The 4 pin wiring diagram is a commonly used wiring setup for trailers. It consists of four wires, each with a different color and function. The four pins are connected to the following components:

Pin Color Function
1 White Ground
2 Brown Taillights
3 Yellow Left Turn/Brake
4 Green Right Turn/Brake

The white wire is connected to the vehicle’s ground, while the brown wire controls the taillights. The yellow wire controls the left turn and brake lights, and the green wire controls the right turn and brake lights.

3. Advantages of the 4 Pin Wiring Diagram

The 4 pin wiring diagram offers several advantages. Firstly, it is a simple and easy-to-understand wiring setup, making it ideal for beginners. Secondly, the 4 pin wiring system is widely supported and compatible with most trailers and towing vehicles. Lastly, it provides the basic functionality required for safe towing, such as taillights and turn signals.

4. Disadvantages of the 4 Pin Wiring Diagram

While the 4 pin wiring diagram is popular, it does have some limitations. One of the main drawbacks is its limited functionality. The 4 pin setup only provides basic lighting and turn signal control, and it may not be suitable for trailers with additional electrical components or features.

5. Alternative Wiring Options

If the 4 pin wiring diagram doesn’t meet your needs, there are alternative options available. One common alternative is the 7 pin wiring diagram, which offers more functionality and is commonly used for larger trailers. The 7 pin setup includes additional pins for features like electric brakes, auxiliary power, and reverse lights.


Q: Can I use the 4 pin wiring diagram for a trailer with brakes?

A: No, the 4 pin wiring diagram does not support electric brakes. You would need to use a wiring setup that includes additional pins, such as the 7 pin wiring diagram.

Q: How do I connect the 4 pin wiring harness to my vehicle?

A: The 4 pin wiring harness typically plugs into a connector located near the vehicle’s rear bumper. Simply match the corresponding colors of the wires and connect them securely.


In conclusion, the 4 pin wiring diagram is a simple and widely used setup for trailers. It provides basic lighting and turn signal control, making it suitable for most towing needs. However, if you require additional functionality, such as electric brakes, you may need to consider alternative wiring options like the 7 pin setup. Ensure to choose the wiring diagram that best suits your trailer’s requirements and enjoy safe and hassle-free towing!