If you own a 2015 GMC Sierra and are planning to haul a trailer, it’s important to understand the trailer wiring system. A properly installed and functioning trailer wiring system ensures that the trailer’s lights, brakes, and other electrical components work correctly.
What is a Trailer Wiring Diagram?
A trailer wiring diagram is a schematic drawing that shows the electrical connections between the trailer and the towing vehicle. It provides a visual guide on how to connect the wiring harness and what color wires to match. A trailer wiring diagram is essential for installing and troubleshooting the trailer wiring system.
Why Do You Need a Trailer Wiring Diagram for Your 2015 GMC Sierra?
The 2015 GMC Sierra comes with a towing package that includes a factory-installed hitch receiver and a seven-pin connector. However, the trailer wiring system is not included in the package, and it must be installed separately. To ensure that the trailer wiring system is installed correctly, a trailer wiring diagram is needed.
Understanding the Trailer Wiring System
The trailer wiring system consists of several components, including the wiring harness, the trailer connector, and the trailer’s electrical components.
The Wiring Harness
The wiring harness is a set of wires that run from the towing vehicle’s electrical system to the trailer’s electrical system. The wiring harness typically includes the following wires:
| Wire Color | Description |
|---|---|
| White | Ground wire |
| Brown | Taillights |
| Yellow | Left turn/brake lights |
| Green | Right turn/brake lights |
| Blue | Electric brakes |
The wiring harness may also include additional wires for other trailer components, such as backup lights, electric trailer brakes, or a battery charging system.
The Trailer Connector
The trailer connector is the device that connects the trailer’s electrical system to the towing vehicle’s electrical system. The 2015 GMC Sierra comes with a seven-pin connector, which provides the following connections:
| Pin | Description |
|---|---|
| 1 | Ground |
| 2 | Backup lights |
| 3 | Electric brakes |
| 4 | Taillights |
| 5 | Left turn/brake lights |
| 6 | Right turn/brake lights |
| 7 | Battery charging |
The Trailer’s Electrical Components
The trailer’s electrical components include the taillights, the brake lights, the turn signals, and the electric brakes (if equipped). These components must be connected to the wiring harness and the trailer connector according to the trailer wiring diagram.
How to Install the Trailer Wiring System on Your 2015 GMC Sierra
The following steps outline how to install the trailer wiring system on your 2015 GMC Sierra:
Step 1: Gather the Necessary Tools and Materials
You will need the following tools and materials:
- Trailer wiring kit
- Wire cutters
- Wire strippers
- Electrical tape
- Zip ties
- A multimeter (optional)
Step 2: Find the Trailer Wiring Connector
Locate the trailer wiring connector on the back of your 2015 GMC Sierra. The connector is typically located near the hitch receiver.
Step 3: Install the Wiring Harness
Install the wiring harness according to the trailer wiring diagram. Connect the white wire to the ground, the brown wire to the taillights, the yellow wire to the left turn/brake lights, the green wire to the right turn/brake lights, and the blue wire to the electric brakes (if equipped).
Step 4: Connect the Trailer Connector
Connect the trailer connector to the wiring harness, matching the wires according to the trailer wiring diagram. Use zip ties to secure the wires and prevent them from getting tangled or damaged.
Step 5: Test the Trailer Wiring System
Test the trailer wiring system to ensure that all the lights and electrical components are working correctly. Use a multimeter (if equipped) to check the voltage across the wires and ensure that there are no shorts or other electrical problems.
FAQ
What is a trailer brake controller?
A trailer brake controller is a device that regulates the electric brakes on the trailer. It applies the brakes in proportion to the towing vehicle’s braking force, helping to slow down the trailer and prevent it from swaying or jackknifing.
Do I need a trailer brake controller for my 2015 GMC Sierra?
It depends on the weight of the trailer and the state’s towing laws. In general, if the trailer weighs more than 1,500 pounds, a trailer brake controller is required. Check your state’s towing laws for specific requirements.
How do I install a trailer brake controller?
The installation process varies depending on the specific brake controller and your 2015 GMC Sierra’s electrical system. Consult the brake controller’s instructions and the trailer wiring diagram for guidance.
What are the consequences of an improperly installed trailer wiring system?
An improperly installed trailer wiring system can cause a variety of problems, including:
- Non-functioning lights
- Overheating electrical components
- Short circuits
- Damage to the towing vehicle’s electrical system
- Unsafe towing conditions
What should I do if I’m having trouble with my trailer wiring system?
If you’re having trouble with your trailer wiring system, consult the trailer wiring diagram and check the connections and electrical components. If you’re still having problems, take your 2015 GMC Sierra and trailer to a qualified mechanic for inspection and repair.
