The Pontiac G5 brake light requires a 3157 bulb size for proper installation and function within the rear lighting assembly. Data for the specified component covers the range from 2007 to 2009.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Pontiac G5 uses two distinct bulb types across its brake lighting system for the 2007-2009 model years: the 3157 for the standard brake lights and the 912 for the center high mount stop light.
The 3157 is a dual-filament wedge bulb operating at 12V with a wattage split of 27W for the high-intensity filament and 7W for the low-intensity filament, which allows a single bulb to serve both brake and running light functions.
The T25 designation on the 3157 refers to its wedge base size, a physical characteristic that determines socket compatibility and is not interchangeable with other wedge base sizes.
The 912 is a single-filament wedge bulb rated at 12V and 12W, conforming to the T15 wedge base form factor.
The 912 is classified as a variant of the 921 bulb. While the two share the same T15 base and 12V rating, the 921 operates at a higher wattage of 16W, making them functionally distinct despite their physical similarity.
Both the 3157 and 912 conform to ANSI standards applicable in the United States and Canada, indicating standardized electrical and physical tolerances across manufacturers producing these bulb types.
The dual-filament design of the 3157 means that substituting it with a single-filament bulb of otherwise similar specifications would result in the loss of one lighting function, as the socket is wired to address both filaments independently.
The center high mount stop light on the Pontiac G5 (2007-2009) uses the 912 exclusively, a bulb type separate from the 3157 used at the rear brake positions, reflecting a difference in the optical and spatial requirements of each lamp housing.