Parts for your GMC Sierra 1500
GMC Sierra 1500 Third Brake Lights
Buy GMC Sierra 1500 third brake lights online, from a single 921 bulb to a complete center high mount stop lamp with cargo lights. Our 8 options cover 1999-2017 trucks and range from $2.72 to $155.97. Brands include AC Delco, Dorman, Anzo, Action Crash and Brock, and each listing shows the cab and engine fitment it was cataloged for.
Year
More GMC Sierra 1500 parts
Which Sierra lamp fits your cab
The third brake light sits at the top center of the cab, above the rear window, and on most Sierra 1500 trucks it shares a housing with the cargo lamps. There are three main designs in these years: the 1999-2006 GMT800 lamp, the 2007-2013 GMT900 lamp and the 2014-2017 K2XX lamp. They do not interchange across generations.
Cab style can change the housing, mounting or wiring, so confirm regular, extended or crew cab. Drive type and engine do not usually decide the lamp. Before you order, compare lens shape, mounting hole spacing, connector terminals and the bulb or LED layout with the lamp on your truck.
Why Sierra third brake lights fail
Water is the most common problem. The perimeter gasket that seals the lamp to the cab breaks down with age, and water then gets into the housing or drips into the cab near the headliner. This is a documented issue on 2014-2017 trucks.
Other signs are a brake or cargo lamp that will not light or works only some of the time, a cracked or cloudy lens, corrosion inside the housing, and moisture behind the lens. A burned-out bulb can look exactly like a failed housing, so on bulb-type lamps try a new bulb first. A 921 bulb is used for the brake function on some later lamps.
Bulb, gasket or full assembly
Decide what you actually need. A bulb-only fix costs a few dollars. A leaking lamp needs at least a new gasket, and a cracked or corroded housing needs a full assembly. Some later assemblies are not serviceable, so the whole lamp is replaced. Check whether the gasket is included in the listing.
On 2014-2017 trucks the lamp comes off with two T20 Torx screws, then you unplug the connector. Clean the mounting surface on the cab before fitting the new gasket and housing. Test the brake and cargo lamps before you fully tighten the screws, and look for moisture or corrosion at the connector and headliner if the old lamp leaked.
More about third brake lights
Read our third brake lights buying guide for how the part works and what to look for in any vehicle.
Sierra 1500 questions
Is the third brake light the same on all 2007-2013 Sierra 1500 cabs?
Not always. Regular, extended and crew cab trucks can use different housings, mounting details or connectors within the same generation. Match your cab style and compare the connector and lens shape with your original lamp before you buy.
Why is water leaking from my Sierra third brake light?
The usual cause is a worn or cracked perimeter gasket between the lamp and the cab. Replacing the gasket, or the full lamp if the housing is damaged, stops the leak. Check the headliner area and connector for moisture damage.
What bulb does a GMC Sierra 1500 third brake light use?
It depends on the generation. Some lamps take a replaceable bulb, and the brake function uses a 921 bulb in some later applications, while other assemblies are sealed and replaced as a unit. Check your original lamp and the listing details.