The 2003 GMC Envoy uses standard halogen bulbs for its brake lights. The bulbs are mounted within the tail light assembly, which must be removed to access the bulbs. There are two primary brake lights on the Envoy's rear. There is also a small, third brake light above the glass window of the lift gate. This brake light is not serviceable; the entire panel must be removed (dealer replacement is recommended). The standard brake lights, however, can be replaced at home.
With the vehicle off, open the rear lift gate. Remove the two screws from the exposed edge of the tail light assembly.
Pull the tail light assembly away from the Envoy. Unplug the wiring harness attached to the assembly.
Remove the three screws mounting the triple bulb socket to the assembly. Pull the socket away from the assembly.
Pull the old brake light bulb straight up to remove it. Using gloves, insert the new bulb into the assembly.
Reattach the socket to the assembly. Tighten the three screws and reconnect the wiring harness. Position the assembly back in place and tighten the two screws to secure it.
