Chevrolet Monte Carlo Back Up Light Bulb Size

The Chevrolet Monte Carlo back up light utilizes 921, 3057, 3156, 1156, and P21W bulb sizes depending on the specific production period for the vehicle. Available data covers a range from 1970 through 2007 for the components listed in the provided specifications.

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
2000-2007	921
1996-1999	3057
1995	3156
1970-1988	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
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). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Chevrolet Monte Carlo back up light specifications span model years 1970 through 2007, with four distinct bulb types used across that range: the 921, 3057, 3156, and 1156.
The 1156 is the most frequently specified bulb across the listed years, covering the Monte Carlo from 1970-1988. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W.
The BA15s bayonet base on the 1156 is a twist-and-lock mount, which is physically incompatible with the wedge-style base found on the 921, 3057, and 3156 bulbs used in later model years.
The 921 is the second most frequently specified bulb, covering the Monte Carlo from 2000-2007. It is a T15 wedge bulb rated at 12V and 16W, making it the lowest-wattage back up light bulb in the specifications.
The 3057 is a dual-filament T25 wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament. It is specified for the Monte Carlo for 1996-1999.
Although the 3057 carries a dual-filament design, its role in the back up light position uses only one of those filaments. The secondary 7W filament is a characteristic of the bulb type itself rather than a functional requirement of the back up light application.
The 3156 is a single-filament T25 wedge bulb rated at 12V and 27W, specified solely for the 1995 Monte Carlo. It shares the same T25 wedge form factor as the 3057 but lacks the secondary filament.
The T25 wedge base shared by the 3057 and 3156 is physically larger than the T15 wedge base of the 921, meaning these bulb types are not interchangeable despite both using a wedge-style mount.
All four bulb types in the specifications conform to ANSI standards applicable in both the United States and Canada.
The 1995 Monte Carlo stands as the only model year in the specifications assigned the 3156, placing it as a transitional year between the 3057 used in 1996-1999 and the earlier 1156 generation.