Troubleshooting Wiring on Trailer Towed by 2009 GMC Acadia With Tow Package  

Question:

Helpful Expert Reply:

Since you did not find any blown fuses, my suspicion is that the problem lies somewhere in the wiring of the trailer, so let's begin by isolating the problem to confirm that the problem lies in the trailer wiring. Use a circuit tester like part # PTW2993 on the trailer connector as each lighting function is activated. Activate the right turn signal, then test the pins on the connector. Do the same for the left turn, brake and running lamp.

If the trailer connector checks out okay, then you have ruled out the vehicle as being the problem. You will need to closely examine the wiring on the trailer, beginning with the trailer connector that plugs into the socket on the vehicle. Check for green or white corrosion on the metal contacts of the connector. In some cases, the corrosion can spread internally to where the wire attaches to the terminals, preventing the current from flowing to the trailer lamps. Clean or replace the connector as necessary. Also, check the grounding point on the trailer where the white wire from the connector attaches to the trailer frame, which is typically located on the trailer tongue. Make sure the ground connection is secure and not corroded. You should also check the ground points for each individual lamp, making sure that each lamp is grounded to the trailer frame via its mounting studs or by ground wire from the lamp to the trailer frame.

If your testing indicates that the trailer connector on the vehicle is not working correctly, consult your owner's manual to make sure you are checking the correct fuses, as vehicles can have fuse boxes in multiple locations.

I have linked you to an FAQ article on wiring troubleshooting. After checking the items mentioned above and running through the procedures in the FAQ article, if you cannot locate the problem, let me know and we will check some other possibilities.

expert reply by: Mike L

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