Troubleshooting 7-Way to 4-Way Adapter that Works on One Vehicle But not Other
Updated 10/19/2015 | Published 10/18/2015
Question:
I have 2 vehicles, a 06 GMC Sierra 1500 and a 06 GMC envoy Denali. Both have factory 7 pins plugs under the bumpers. I have a 7 pin to 4 flat adapter that I use on the Sierra and my trailer running lights, turn signals and brakes all work fine. I tried using the same adapter and trailer on my envoy and had only left turn signal. No brake lights or running lights. Isnt trailer wiring on a 7 pin all standard? Is it different for an Envoy to where Ill need a different adapter for the envoy to connect correctly or is it possible the envoys 7 pin is wired incorrectly? Thx
asked by: Justin
Helpful Expert Reply:
The 7-ways on both your 2006 GMC Sierra and Envoy would be pinned out the exact same way. What you are experiencing is most likely due to corrosion on the pins of the Envoy.
Try hitting the pins of the 7-way on your Envoy with fine grit sandpaper and making sure none of them are bend back and trying the adapter again. You can also test the pins with a circuit tester like part # PTW2993 to see if voltage is on all of the pins in the correct spot when the taillight circuits are applied like in the video I attached.
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