Introduction
The CURT 56338 Vehicle-Side Custom 4-Pin Trailer Wiring Harness is designed to provide a simple and reliable electrical connection for towing. This custom wiring connector, also known as a T-connector, utilizes existing factory wiring on your vehicle, eliminating the need for cutting, splicing, or soldering. It provides a standard 4-way flat connection for trailer tail lights, brake signal lights, and turn signals. This product is specifically designed for select years of the Mazda CX-9.
Image: Overview of the CURT 56338 Trailer Wiring Harness components, including the main module, wiring, 4-pin connector, fuse holder, and dust cover.
Setup and Installation
This wiring harness is designed for easy, plug-and-play installation. No special tools are typically required beyond basic hand tools for accessing vehicle wiring points.
- Locate Vehicle Wiring Socket: Identify the existing factory wiring socket on your Mazda CX-9. This harness is designed to plug directly into this OEM-compatible socket.
- Connect the Harness: Plug the vehicle-specific connector of the CURT harness into the factory wiring socket. Ensure a secure and firm connection.
- Route Wiring: Carefully route the wiring harness to the rear of the vehicle where the trailer connection will be made. Secure the wiring using the provided zip ties to prevent snagging or damage.
- Install Fuse: Insert the provided fuse into the fuse holder integrated into the harness. This protects the circuit.
- Secure the Module: Mount the electronic module in a dry, secure location within the vehicle, away from moving parts or excessive heat.
- Prepare 4-Way Flat Connector: The harness provides a standard 4-way flat connector for your trailer. This connector is designed to mate with the trailer's corresponding 4-way flat plug.
Image: Illustration showing the plug-and-play connector and its connection point to the existing socket on the vehicle.
Image: Various components of the harness, including the fuse, terminals, and zip ties, which are used for installation and circuit protection.
Image: Close-up view of the standard 4-way flat trailer wiring output, showing the male and female connection points.
Image: Diagram illustrating the pin configuration of a 4-way flat vehicle end connector.
Operating Instructions
Once installed, using the CURT 4-pin wiring harness is straightforward:
- Connecting to Trailer: Align the 4-way flat connector from your vehicle's harness with the corresponding 4-way flat plug on your trailer. Push them firmly together until they are securely connected.
- Testing Lights: Before driving, always test all trailer lights (tail lights, brake lights, turn signals) to ensure they are functioning correctly.
- Using the Dust Cover: When the wiring harness is not in use and disconnected from a trailer, place the included rubber dust cover over the 4-way flat connector. This protects the terminals from dirt, moisture, and corrosion.
Image: A hand demonstrating how to apply the rubber dust cover to the 4-way flat connector for protection when not in use.
Maintenance
Regular maintenance ensures the longevity and reliable performance of your wiring harness:
- Periodic Inspection: Inspect the wiring harness, especially the connectors and visible wires, periodically and before each towing trip. Look for any signs of wear, fraying, cuts, or corrosion.
- Keep Connectors Clean: Ensure the 4-way flat connector and its terminals are clean and free of dirt, debris, or corrosion. Use a dielectric grease on the terminals for added protection against moisture and corrosion.
- Use Dust Cover: Always use the provided dust cover when the harness is not connected to a trailer to protect the terminals from environmental elements.
- Secure Wiring: Verify that all wiring is securely fastened and not dangling or at risk of being pinched or abraded.
Troubleshooting
The CURT wiring harness features a circuit-protected converter system designed to prevent damage to your tow vehicle. If you experience issues with your trailer lights, follow these troubleshooting steps:
If Trailer Lamps Light for a Few Seconds and Then Go Off:
- Check Ground Wire: Inspect the ground wire connection on both the harness and the trailer for looseness or corrosion.
- Check for Overload: Verify that the trailer is not drawing too much current (e.g., too many bulbs or a short circuit). The module is designed to shut down in overload situations to protect the vehicle.
- Reset Circuit: If the tow vehicle lamps are working but trailer lamps are not, turn off power to the faulted circuit for a few seconds, then try again. If the trailer lamps return to normal function, the fault has been corrected.
If the Circuit Fails to Light:
- Check Tow Vehicle Fuses: Ensure all relevant fuses in your tow vehicle's fuse box are intact and not blown.
- Inspect Plug-in/Pin Connections: Confirm that all connections, especially the main plug-in to the vehicle's factory socket and the 4-way flat connection to the trailer, are secure and clean.
- Check for Defective Bulbs: Inspect all bulbs on the trailer for damage or burnout. Replace any defective bulbs.
- Check Ground Wire: Re-check the ground wire connections on both the harness and the trailer.
- Locate and Correct a Short: A short circuit can prevent lights from working. Inspect wiring for any exposed or damaged sections that might be touching metal.
Note: Using a circuit tester can help confirm system function. If problems persist after following these steps, consult a qualified installer or contact CURT customer support.
Specifications
| Feature | Detail |
|---|---|
| Brand | CURT |
| Model Number | 56338 |
| Product Type | Vehicle-Side Custom 4-Pin Trailer Wiring Harness |
| Compatibility | Select Mazda CX-9 years |
| Connector Type | 4-Way Flat |
| Installation | Plug-and-Play (No cutting, no splicing) |
| Circuit Protection | Built-in electronic module with internal circuit protection |
| Included Accessories | Dust cover, fuse, zip ties |
| Item Weight | 13.7 ounces |
| Product Dimensions | 11 x 3 x 9 inches |
| Country of Origin | USA |
Safety Information
CALIFORNIA WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov
Always inspect wiring periodically, before towing, and frequently while towing to ensure safe operation.
Warranty and Support
For specific warranty information regarding your CURT 56338 Trailer Wiring Harness, please refer to the documentation included with your purchase or visit the official CURT website. For technical assistance, troubleshooting beyond this manual, or to inquire about replacement parts, please contact CURT customer support directly.
You can find more information and support resources by visiting the CURT Store on Amazon.
