Troubleshooting Running Light Circuit on Wiring for 2011 Mazda CX 9 Trailer Harness
Question:
All lights on the trailer except the tail and license plate light, so I assume there is some faultinch in the connectors. I dont understand why all other light functions turn signals, brake lights, hazard lights work and have power, but no tail lights do not. Ideas or suggestions? Thanks.
asked by: Gerald S
Helpful Expert Reply:
The most common cause for some trailer light functions to operate while others do not is a bad ground connection at either the vehicle wiring harness or the trailer-side wiring. This can happen because a weak ground will still allow some current to pass through - say enough for brake lights and turn signals that are not on all the time - but not for other functions like the running lights and license plate light that ARE on continuously.
Check that the white ground wire's ring terminal on the CX-9's harness is tightly affixed to a clean bare metal surface that is free of paint, primer, grease or corrosion. You can use a touch of sand paper if needed to clean up the wire's attachment point. Also check that the trailer's ground wire is similarly attached to a clean bare metal surface on the trailer.
If that does not correct the problem check both vehicle and trailer connectors for any signs of trapped dirt, water or even slight greenish or whitish corrosion - any of which could interfere with signal transmission.
You can also test the trailer lights directly by applying 12V power to the pin for the running light circuit, which is most often carried on a brown wire. If the lights work when you give them a direct power input then you know the issue is on the vehicle side or within the connector.
Dielectric grease like # 11755 is a great way to protect those ground connections once everything is working.
Products Referenced in This Question
Dielectric Grease for Electrical Connectors, 2 oz.
- Accessories and Parts
- Trailer Wiring
- Wiring
- Dielectric Grease
- LubriMatic
more information >
Product Page this Question was Asked From
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Powered Converter
- Custom Fit
- 4 Flat
- Tekonsha
more information >
Featured Help Information
Instructions
Miscellaneous Media
Continue Researching
- Shop: Trailer Wiring
- Shop: Trailer Hitch
- Shop: Draw-Tite Max-Frame Trailer Hitch Receiver - Custom Fit - Class III - 2"
- Shop: etrailer Trailer Hitch Receiver - Custom Fit - Matte Black Finish - Class III - 2"
- Shop: Curt Trailer Hitch Receiver - Custom Fit - Class III - 2"
- Shop: No-Drill Mount for Electrical Mounting Bracket - Short
- Shop: T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Search Results: trailer wiring harness
- Q&A: Options for Running the Power Wire for the Tow Ready Custom Fit Wiring # 118520 on a 2011 Mazda CX9
- Q&A: Difference Between Curt and Draw-Tite Trailer Hitches for 2012 Mazda CX-9
- Video: Best 2011 Mazda CX-9 Trailer Wiring Options
- Article: Routing the Power Wire for a Trailer Wiring Harness
- Shop: Floor Mats
- Shop: Vehicle Lights
- Q&A: Recommended Trailer Hitch For A 2010 Mazda CX-9 Using A Thule Trailway 4 Bike Rack
- Q&A: Spare Tire Operation with Curt Trailer Hitch 13575 Installed on 2015 Mazda CX-9
- Q&A: What is the Towing Prep Package on a 2010 Mazda CX-9 and Does it Include Trailer Wiring
- Search Results: trailer hitch
- Video: Choosing the Right Trailer Wiring
- Shop: Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector
- Q&A: What is the Difference Between a Class II and a Class III Hitch?
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Search Results: trailer hitch wiring
- Article: How to Choose the Right Trailer Hitch Class
- Article: Trailer Wiring Diagrams
- Video: Curt 4-Pole Flat Trailer Connector Mounting Bracket Review
- Shop: Brake Controller
- Search Results: hitch
on Custom Fit Vehicle Wiring
