Geo Metro Back Up Light Bulb Size

The Geo Metro back up light uses bulb sizes 921, 1156, and P21W depending on the specific version of the component. Provided information covers the range from 1989 to 1997.

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
1993-1997	921
1989-1992	1156

Bulb Specifications

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

Other Locations

Additional Notes

The Geo Metro uses two distinct bulb sizes across its model years for the back up light: the 921 and the 1156.
The 921 bulb is a T15 wedge-type unit rated at 12V and 16W, conforming to ANSI standards for the US and Canada.
The 1156 bulb is a single-filament unit with a BA15s bayonet base, rated at 12V and 21W, also conforming to ANSI standards for the US and Canada.
The Geo Metro (1993-1997) takes the 921 bulb for the back up light position.
The 1989-1992 Metro takes the 1156 bulb for the same position.
The two bulb types are not interchangeable. The 921 uses a wedge base, while the 1156 uses a BA15s bayonet base, making the mounting mechanisms physically incompatible.
The 1156 carries a higher wattage at 21W compared to the 921 at 16W, meaning the two bulbs also differ in power draw.