GMC Envoy XL front turn signal bulbs use 3457 size while rear turn signal bulbs use 3057 or 3157 size. The replacement chart covers 2002 through 2006 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC Envoy XL uses two distinct bulb types across its front and rear turn signal positions, with the front position standardized on the 3457 across all model years from 2002-2006, while the rear position splits between two different bulb types depending on the year.
The 3457, 3057, and 3157 are all ANSI-standardized bulbs recognized in both the United States and Canada, sharing an identical T25 wedge form factor and identical electrical ratings of 12V with a dual-filament output of 27W and 7W.
Because all three bulb types share the same T25 wedge base and voltage rating, physical installation across sockets of the same base type is possible, though each part number carries specific performance and circuit-matching characteristics that distinguish it from the others.
The dual-filament design of these bulbs means a single unit serves two lighting functions within one socket, with the higher 27W filament typically handling the active turn signal flash and the lower 7W filament serving a secondary role such as a running or parking light.
The rear turn signal of the Envoy XL shifted from the 3157 in 2002-2003 to the 3057 in 2004-2006, making year verification necessary before sourcing a rear replacement bulb.
Despite the 3057 and 3157 sharing the same T25 base and wattage ratings, they are not considered interchangeable replacements in all applications, as differences in filament positioning and contact orientation can affect circuit compatibility depending on the socket design.
The front turn signal position on the Envoy XL remained consistent with the 3457 across the full 2002-2006 production span, indicating no mid-cycle revision to that socket specification.
The 3457 and 3057 share the same wattage output and base type but differ in internal construction details, which is why they carry separate ANSI part numbers despite appearing functionally similar in specification tables.