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Troubleshooting 4-Way Not Functioning on a 2000 GMC Sierra


How to troubleshot no power to 4 pin connector on 7 pin connector in a 2000 GMC Sierra slt


Expert Reply:

To make sure the problem is isolated to the trailer, I recommend using a simple light tester, like part # 40376, to test the trailer connector on your tow vehicle to make sure it is functioning properly. I have attached a video that shows how to do this. If the connector on your vehicle is not functioning as it should, then the problem could be related to a poor connection or faulty wiring on your vehicle. If this is the case, you can send me the year, make, and model of your vehicle and the problems you found during testing and I would be happy to come up with a solution for you.

First, inspect the connectors on the trailer and the vehicle for corrosion and repair or replace as necessary. Next, check the ground connections on the trailer. A poor ground could cause the lights to malfunction. Be sure to check the main trailer ground and the grounds for each light assembly if they are accessible. If possible, it is best to route all of the ground wires back to the main trailer ground, but this may be difficult if the wires are hidden behind wall panels on your camper. If the wires are not accessible and you aren't comfortable removing wall panels, I recommend taking your trailer to a trailer shop.

If all of the ground connections are good and you do not see any corrosion, inspect the wiring for any potential shorts that could cause power to jump between the tail light wires. Follow the wires from the trailer connector all the way back to the tail lights looking for any pinched, frayed or damages sections of wire and repair or replace and needed.

I have attached a link to our trailer wiring help article that gives general trailer wiring information and troubleshooting.

expert reply by:
Jameson C

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