Replacing the Third Brake Light and Preventing Cab Leaks on a 2005 GMC Sierra 1500

Replacing the third brake light on a 2005 Sierra is a simple job. Open the rear door and look at the top of the cab exterior, just above the rear window. You will see two screws holding the light housing in place. Use a Torx driver (usually T15 or T20) to remove these screws. The housing may feel stuck because the old foam gasket has essentially glued itself to the paint. Do not pry with a metal screwdriver—this will scratch the paint. Instead, gently rock the housing side-to-side or use a plastic trim tool to break the seal. Lift the housing up and disconnect the wiring harness by pressing the release tab. Set the old light aside.
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