4 Pin Trailer Plug Wiring Diagram

Hello and welcome to our article on the 4 pin trailer plug wiring diagram. If you are a trailer owner or planning to become one, understanding the wiring diagram is crucial for a safe and efficient towing experience. In this article, we will provide you with a detailed explanation of the 4 pin trailer plug wiring diagram, its advantages, disadvantages, and alternative options.

Sub Title 1: Understanding the Basics

Before we dive into the wiring diagram, let’s quickly go over the basics. A 4 pin trailer plug is commonly used for small trailers, utility trailers, or boats. It provides power to the trailer’s lights, turn signals, and brake lights. The four pins on the plug correspond to the following functions:

Pin Function
1 Ground
2 Left Turn/Brake Lights
3 Right Turn/Brake Lights
4 Tail Lights

It is important to note that the 4 pin trailer plug is not compatible with trailers that require additional features such as reverse lights or electric brakes. For those trailers, a 7 pin plug or higher is necessary.

Sub Title 2: Wiring Diagram

Now, let’s take a closer look at the wiring diagram for the 4 pin trailer plug. Please refer to the table below for a detailed explanation of each wire:

Wire Color Function
White Ground
Yellow Left Turn/Brake Lights
Green Right Turn/Brake Lights
Brown Tail Lights

To properly connect the wires, you will need to match the corresponding color on the trailer plug to the color on the trailer’s wiring harness. Securely connect each wire using butt connectors or heat shrink tubing to ensure a reliable connection.

Sub Title 3: Advantages of the 4 Pin Trailer Plug Wiring Diagram

The 4 pin trailer plug wiring diagram offers several advantages:

  • Simplicity: The 4 pin wiring system is straightforward and easy to understand, making it ideal for beginners.
  • Wide Availability: The 4 pin plug is widely available and compatible with most trailers, making it convenient for trailer owners.
  • Cost-Effective: Compared to higher pin configurations, the 4 pin plug is more affordable, making it a budget-friendly option.

Sub Title 4: Disadvantages of the 4 Pin Trailer Plug Wiring Diagram

While the 4 pin trailer plug wiring diagram has its advantages, it also has a few limitations:

  • Limited Functionality: The 4 pin plug is only suitable for basic lighting functions and does not support additional features like electric brakes or reverse lights.
  • Lower Power Capacity: The 4 pin wiring system has a lower power capacity compared to higher pin configurations, which may limit its use for larger trailers.

Sub Title 5: Alternative Options

If your trailer requires additional features not supported by the 4 pin plug, you have a few alternative options:

  • 7 Pin Plug: The 7 pin plug is the most common alternative and provides additional functionalities like electric brakes and reverse lights.
  • Custom Wiring: For trailers with unique requirements, custom wiring solutions can be implemented to accommodate specific needs.

FAQ (Frequently Asked Questions)

Q: Can I use a 4 pin trailer plug for my camper trailer?

A: It depends on the electrical requirements of your camper trailer. If it only requires basic lighting functions, the 4 pin plug should suffice. However, if your camper trailer has additional features, you may need a higher pin configuration.

Q: How do I troubleshoot issues with my 4 pin trailer plug wiring?

A: Start by checking the connections and ensuring they are secure and free from corrosion. If the issue persists, use a multimeter to test for continuity and voltage at each wire connection.


In conclusion, the 4 pin trailer plug wiring diagram is a simple and widely available solution for trailers that require basic lighting functions. It is easy to understand, affordable, and suitable for small trailers. However, it has limitations in terms of functionality and power capacity. If your trailer requires additional features, consider alternative options such as the 7 pin plug or custom wiring. Remember to always follow the wiring diagram and ensure proper connections for a safe towing experience.