Chevrolet Malibu Back Up Light Bulb Size

The Chevrolet Malibu back up light utilizes bulb sizes 921, 3057, 1156, and P21W for various lighting applications. Available data for the specified components covers the span from 1964 through 2024.

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
2023-2024	921
2016-2021	921
2004-2007	921
1997-2003	3057
1973-1983	1156
1964-1967	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 bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Chevrolet Malibu back up light specifications reference three distinct bulb types across its model years: the 921, the 3057, and the 1156.
The 921 is a T15 wedge-base bulb rated at 12V and 16W under the ANSI standard applicable in the US and Canada. It is the specified back up light bulb for the Chevrolet Malibu from 2016-2024, as well as for the 2004-2007 model years.
The T15 designation refers to the tubular bulb shape, with the number indicating its width in eighths of an inch. The wedge base design means the glass envelope itself acts as the retention mechanism, with no separate metal base required.
The 3057 is a T25 wedge-base bulb rated at 12V with a dual-filament configuration drawing 27W on the high filament and 7W on the low filament. It carries the ANSI standard for the US and Canada and is specified for the Chevrolet Malibu from 1997-2003.
Although the 3057 is a dual-filament bulb, its role in this application is limited to back up light function. The presence of two filaments does not imply a secondary lighting function in this context.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W under the ANSI standard for the US and Canada. It is specified for the Chevrolet Malibu from 1964-1967 and again from 1973-1983.
The BA15s bayonet base uses a 15mm base width with a single contact pin, distinguishing it from dual-pin bayonet variants. This base type is not interchangeable with the wedge-base designs used in the 921 and 3057 bulbs.
The 921 and 3057 are both wedge-base bulbs, but they are not interchangeable. The T15 and T25 designations indicate different physical sizes, and their wattage ratings differ, making cross-substitution outside of manufacturer specifications inadvisable.
The three bulb types specified across the Malibu's history represent three physically distinct base and housing configurations, meaning fitment is generation-specific and not transferable across the different eras of the model.
All three bulb types listed in the specifications conform to ANSI standards recognized in both the United States and Canada, indicating consistent regulatory compliance across the applicable model years.