No Running Lights With T-One 4-Pole Harness # 118451 on 2009 Acadia XLT with Tow Package  

Question:

Expert Reply:

The wiring harness you referenced, T-One 4-Pole Harness # 118451 from TowReady, uses plug-and-play connections to your Acadia taillight assemblies to generate lighting signals for your trailer. This harness provides trailer lighting signals on its included 4-pole connector that are completely independent of any factory tow package wiring that may be in place. Please take a look at the linked video which shows installation of this harness in your same year/make/model vehicle. The written instructions are also included.

If you have stop and turn signals on your 4-pole but not running lights, then the ground connection is suspect. Stop and turn signals are not constant signals so they do not draw as much power as running lights. If your ground connection is weak, it may be able to pass enough current for these signals but not enough for the running lights. Carefully check that the white ground wire ring terminal is firmly attached to a clean unpainted metal surface. You can use sandpaper to remove paint if necessary to provide a good connection point, or you can use an existing grounding point behind the driver-side taillight assembly. This ground wire must be very firmly attached in order to allow full power delivery to the 4-pole.

Next, I suggest you apply a circuit tester to the 4-pole to confirm that it is carrying the correct running light signals. You can use a tester like # PTW2993. With your trailer disconnected, activate the lights on the Acadia and apply the grounded tester probe to the pin for the brown running light wire. Please refer to the photo provided for where to apply the tester. With the vehicle lights on you should detect a steady signal on the pin for the brown wire. If you do not, then check the harness connection points at the taillights for a connector that is not fully seated. If you do detect the signal, then the problem is somewhere in the trailer, and you will want to focus your troubleshooting on the trailer side.

Carefully inspect the trailer connector for any signs of even slight greenish or whitish discoloration, clean contacts as necessary. Follow the wiring from the trailer connector all the way to the running lights. Check that the trailer ground wire is tightly attached to a clean rust- and paint-free part of the trailer frame and that the wires have no cracks or worn spots in the insulation; repair or replace damaged wires as necessary. Also check the wiring at the running lights themselves to be sure they are well grounded to the trailer frame. Some lights use their mounting stud as the ground point, while others provide a separate ground wire. In either case the ground connection at each running light must also be secure for proper operation. You might also refer to the linked article on troubleshooting 4-pole installations.

expert reply by: Adam R

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