Remove the cover from your third brake light. Take hold of the lightbulb, push in and turn at the same time. The lightbulb will come out.
Need to remove the tailgate inner trim panel on hatch and estate car.The lamp is held on by two clips (estate)or two screws(hatch)the wiring needs a couple of ties undoing to remove the lamp.
with a hammer
The 3rd brake light is set in under the rear glass. Bentley has a superseded lamp assembly that can be installed without removing the rear window. It is a kit, and requires cutting the old one out and gluing the new one to the glass. We have replaced a few here, although not too difficult, you will have to remove the interior headliner to gain access to the connectors. The 3rd brake light is all led and is not serviceable.
You have a bad ground.
01 Yukon 3rd brake light removal......changing the third brake light on a 2001 Yukon is a relatively easy task. First open the rear liftgate (not just the glass). This will expose the two screws that secure the housing of the lamp to the body (it also exposes the connector plug which, obviously, you should unplug). After removing the two screws, separate the rubber housing from the LED lamp itself....and there you have it!...because the third brake light is a sealed lamp the entire brake light must be changed. you can�t just replace the bulbs. ...
If you are referring to the 3rd brake lamp assembly, all you have to do is pull the left side of the plastic mount toward you if you are sitting in the back seat. the assembly pops right out and the bulb can be replaced.
more information needed is it in the window or the design in the spoiler
If it is one of the main side brake lights, open the tail gate, remove the two Philips screws from the side of the lense, and slide the entire light assembly towrds you to remove it from the body. If it is the 3rd brake light in the tail gate, pry the edge facing you up slightly, then pull the cover towrds you to remove it and you will have access to all three bulbs in it.
Remove 2 screws that hold lens on, remove lens, then you should be able to change bulbs without any problems
Unlike the two standard brake light bulbs, which are generally changed from behind, a 'third' brake light is usually changed from the front. Locate the lens mounting screws and remove them; the bulb should then be revealed.
on the hatch back there is a cover on the door under the light remove it. there are three screws that hold the 3rd light on remove them. unhook the wire harness. remove the small screws from the 3rd light and pull it open. there you can unscrew the light and replace it.
The lens is held on with two t25 screws. Remove them, pull lens of, reverse to install.