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Troubleshooting Trailer Brake and Turn Signals Not Working with Tekonsha T-One Harness on Acadia  


I’m expanding in this question: Does a GMC Acadia Need an Upgraded Fuse Panel to Add Trailer Wiring My issue and question: The harness doesn’t work. The driver side brake light and turn signal doesn’t work. I purchased the fuses for the trailer turn signal and realized there are 2 metal connectors in the fuse box, per 4 prong fuse. Everything I’ve read in the GMC Acadia forum says you need the V92 towing fuse box. I’m only trying to use a 4 prong towing system. I’m including a pic of the missing connectors in the fuse box. Please help.


Expert Reply:

The Tekonsha T-One Vehicle Wiring Harness # 118451 that you referenced plugs in-line with the tail light circuits on your GMC Acadia via factory ports behind the tail lights themselves. The harness and the power it receives from your vehicle should be completely separate from any tow package, as it simply gets power from the factory light circuits. There aren't any fuses related to this harness or its ability to send power back to the trailer lights unless the lights on your Acadia aren't working either.

If the driver's side brake and turn signals aren't working on the trailer when hooked up then I recommend first making sure that the issue is on the vehicle side. You may have already tested the harness in this manner but if not, use a circuit tester like # PTW2979 to test each pin on the 4-Way while you run through the light functions. If you get power at all the appropriate pins then the issue is actually on the trailer.

If this is the case check the trailer's 4-Way for any debris/corrosion that needs to be cleaned out from the pins. Make sure the main harness ground is securely attached to a bare, clean metal surface and that each of the light assemblies are also grounded correctly.

If you didn't get power the Acadia's 4-Way then I recommend making sure the white ground wire from the Tekonsha harness is securely attached to a clean metal surface. It might be worth it to remove the ground connection, sand down the metal where you're attaching it, and re-secure the ring terminal.

If you are still having issues please let me know and we can continue to troubleshoot.

expert reply by:
Chris R

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