The GMC Yukon has a third brake light located at the top of the truck. The third brake gives extra visibility to the driver behind you when braking. Replacing this light will not take long, as it is a sealed assembly and comes right out. The replacement can be purchased at any local automotive parts store.
Open the rear liftgate. Open the entire gate. This will expose the two screws that secure the housing of the lamp to the vehicle.
Unplug the connector by lifting the locking tab and pulling away from the connector. Unscrew the two exposed screws with a Phillips screwdriver.
Separate the rubber boot from the LED lamp. Place the rubber boot around the new lamp.
Screw the lamp to the vehicle with the Phillips screwdriver. Connect the electric connector by pushing it to the other connector until it locks in place.
Close the liftgate. Have an assistant standing behind the truck to advise whether the brake light is working correctly.
