Pontiac Montana Back Up Light Bulb Size

The Pontiac Montana back up light uses 3057, 3156, 2356, and 2456 bulb sizes depending on the specific vehicle configuration. Available data for the lighting components covers the 1999 to 2006 time period.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2006	3057
2005	3156 (With 2 Headlamps)
2005	3057 (With 4 Headlamps)
2004	3156
2003	2356
1999-2002	2456

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3057
ANSI standard (US & Canada). Single-filament wedge bulb (T25). 12V, 27W.	3156
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V.	2356
ANSI standard (US & Canada). Festoon bulb, specialty application. 12V.	2456

Other Locations

Additional Notes

The Pontiac Montana uses four distinct bulb types across its 1999-2006 model years for the back up light position: the 3057, 3156, 2356, and 2456.
The 2456 is the most frequently specified bulb across this range, covering the 1999-2002 model years. It is an ANSI-standard festoon bulb rated at 12V and intended for specialty applications.
The 3057 is a dual-filament wedge bulb in the T25 form factor, rated at 12V with a 27W main filament and a 7W secondary filament. Its dual-filament design means it is not a direct electrical equivalent to single-filament bulbs of similar wattage.
The 3156 is a single-filament wedge bulb, also in the T25 form factor, rated at 12V and 27W. Although it shares the same T25 physical housing as the 3057, the absence of a second filament makes the two bulbs non-interchangeable in applications that rely on dual-filament function.
The 2356 uses a BAY15d bayonet base, which is a physically different mounting type from the wedge base found on the 3057 and 3156. This base difference makes the 2356 incompatible with sockets designed for T25 wedge bulbs.
The 2005 Pontiac Montana has two separate back up light bulb specifications depending on headlamp configuration. Vehicles with two headlamps use the 3156, while vehicles with four headlamps use the 3057.
Because the 2005 model year carries a configuration-dependent fitment, the headlamp count of a specific vehicle must be confirmed before selecting a replacement bulb for that year.
The 2004 Montana specifies the 3156 exclusively, with no configuration-based split, distinguishing it from the 2005 model year despite both years listing the 3156 as a possible fitment.
All four bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating consistent regulatory compliance across the range.
The transition from the 2456 festoon bulb in 2002 to the 2356 bayonet-base bulb in 2003 represents a change in both bulb form factor and base type, meaning parts from those two adjacent model years are not interchangeable.