GMC Envoy Third Brake Light and Moulding (2002-2009)

On a 2002-2009 GMC Envoy, the third brake light (GM calls it the center high-mounted stoplamp, or CHMSL) is a sealed LED assembly at the top of the liftgate, and the moulding is part of that housing. There is no bulb listed for it in GM's owner's manuals, so a cracked moulding, a leaking lens or a dead lamp is fixed by replacing the whole assembly. Before you buy one, check the CHMSL fuse: it is fuse 16 in the rear underseat fuse block.

What the "Moulding" Actually Is

Owners searching for an Envoy third brake light moulding usually mean one of two things:

The lamp housing and lens itself. The stop lamp sits in a long, narrow housing at the top of the liftgate. Sun exposure fades and cracks the plastic over time, and a cracked housing can let water reach the LEDs and the connector.
The trim surrounding it. On the Envoy this area is molded around the lamp, so replacement assemblies are sold as a complete unit that includes the housing, lens and LED board.

Aftermarket listings for the standard 2002-2009 Envoy give the OEM part number as 15201921, the Partslink number as GM2890106, and a Dorman equivalent of 923-204. The same listings cross this lamp to the 2002-2009 Chevrolet TrailBlazer, 2004-2007 Buick Rainier, 2003-2008 Isuzu Ascender, 2002-2004 Oldsmobile Bravada and 2005-2009 Saab 9-7X. Treat those numbers as a starting point and confirm by VIN with a parts counter, because body style matters:

Envoy version	Third brake light fitment
Envoy (standard wheelbase, 2002-2009)	Listed under 15201921 / GM2890106 by aftermarket sellers
Envoy XL (extended wheelbase)	Sold as a separate listing; confirm by VIN
Envoy XUV (sliding roof, drop-down tailgate)	Excluded from the standard listing; different rear design

Step 1: Rule Out the Fuse and Circuit

A dead third brake light is not always the lamp. GM's own fuse charts show two different fuses in play:

Circuit	Fuse	Location (per GM owner's manual)
Third brake light (CHMSL)	16	Rear underseat fuse block, under the rear seat on the driver's side
Stoplamps (main brake lights)	12	Engine compartment fuse block (2008 manual)

The 2002 manual labels fuse 16 "VEH CHMSL" and the 2008 manual labels it "Vehicle Center High-Mounted Stoplamp (CHMSL)," so the location stayed the same across the generation.

Use the symptoms to narrow it down:

Only the third brake light is out. Check fuse 16 first. If it is good, check for power at the lamp connector with a test light while someone presses the pedal. Power present with no light means the lamp assembly has failed.
All brake lights are out. The lamp is unlikely to be the cause. Look at the stoplamp fuse and the brake light switch. Our GMC brake light switch replacement guide walks through that part.
Lights behave oddly together (one lamp dims another, or they stay on). See can one brake light affect another for how shared circuits and grounds cause that.
Brake lights stay on with the pedal released. This usually points to the brake light switch or its adjustment, not the third brake light.

Step 2: Replace the Assembly

The stock Envoy third brake light uses a row of red LEDs behind the lens, not a replaceable bulb, which is why the owner's manuals do not list a bulb number for it. Both the 2002 and 2008 manuals end their bulb tables with a note to contact the dealer for any bulb not listed.

General replacement approach (confirm the exact fastener locations for your year in a service manual):

Open the liftgate and locate the lamp's wiring connector and mounting fasteners from the inside of the liftgate.
Disconnect the connector and remove the fasteners.
Lift the old assembly off, taking care not to scratch the paint around it.
Clean the mounting surface and remove any old sealant or debris so the new gasket seats flat. Poor sealing here is how water gets into the housing and the liftgate.
Fit the new assembly, reconnect the plug and tighten the fasteners evenly.
Test with a helper pressing the brake pedal before you close everything up.

If the old lamp failed because water got in, check the connector pins for corrosion and clean or replace them. A new lamp on a corroded plug can fail the same way.

OE vs Aftermarket Replacement

OE (GM) assembly: the closest match to factory fit and seal. Usually the most expensive option.
Direct-fit aftermarket assembly: sold to replace the OE part number with the factory plug. Quality of the gasket and lens varies by brand, so read the fitment notes and check that the listing states DOT/SAE compliance.
LED "upgrade" styles (smoked or clear lens, full LED strip): these change the look. The lamp still has to meet Federal Motor Vehicle Safety Standard 108, which sets requirements for high-mounted stop lamps, so check the listing's compliance claim, and be aware that heavily smoked lenses may draw attention in states that inspect lighting.

Prices vary widely by brand and region, so compare the exact part number rather than a generic "third brake light" search.

Envoy Rear Lamp Bulbs (For Reference)

While you are working at the back of the truck, these are the rear bulbs GM lists for the lower lamps. The third brake light is not in either table.

Lamp	2002 Envoy manual	2008 Envoy manual
Tail and stoplamps	3057	3157 (back-up, rear turn, stop and tail)
Rear turn signal lamps	3057	3157
License plate lamp	Not listed	W5W

Check the bulb number in your own year's manual or on the old bulb before buying, since the two manuals list different numbers.

Frequently Asked Questions

Does the GMC Envoy third brake light use a bulb?

No replaceable bulb is listed for it. The factory lamp uses LEDs behind the lens, and GM's 2002 and 2008 Envoy owner's manuals do not include a CHMSL bulb in their replacement tables. When it fails, the assembly is replaced.

Where is the third brake light fuse on a GMC Envoy?

Fuse 16 in the rear underseat fuse block, which sits under the rear seat on the driver's side. Both the 2002 and 2008 owner's manuals list it as the CHMSL fuse.

Can I replace just the moulding on the third brake light?

The moulding is part of the lamp housing on the Envoy, and replacement parts are sold as a complete assembly. If the plastic is cracked or faded, replacing the whole unit also restores the seal that keeps water out.

Will an Envoy third brake light fit a TrailBlazer?

Aftermarket sellers list the same part (OEM 15201921, Partslink GM2890106) for the 2002-2009 Envoy and 2002-2009 TrailBlazer, but the extended XL/EXT and XUV versions differ. Confirm by VIN before ordering.

Why does my Envoy third brake light work but the lower brake lights don't?

The two use different fuses. The third brake light runs through fuse 16 under the rear seat, while the 2008 manual lists the main stoplamp fuse as fuse 12 in the engine compartment fuse block. Check the lower bulbs, that fuse, and the brake light switch.