Subaru Impreza Back Up Light Bulb Size

The Subaru Impreza back up light utilizes bulb sizes 1157, 7440, 921, P21W, and 1156 across various production periods. Available data for the specified components covers the range from 1993 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
2024	1157
2017-2019	7440
2015-2016	921
1993-2001	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
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 1156 bulb is the most frequently specified size across the Subaru Impreza backup light fitments in these specifications, covering model years 1993-2001.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and follows the ANSI standard used in the US and Canada.
The 7440 bulb appears in the Subaru Impreza for model years 2017-2019. It is a single-filament T20 wedge bulb rated at 12V and 21W under the same ANSI standard.
Although the 1156 and 7440 share the same 21W power rating, they use entirely different base types, a bayonet base versus a wedge base, making them physically incompatible with each other's sockets.
The 2024 Subaru Impreza specifies the 1157 bulb, which differs from the 1156 in that it carries a dual-filament design and a BAY15d bayonet base rather than the single-filament BA15s base of the 1156.
The BAY15d base of the 1157 has offset pins to prevent incorrect insertion, whereas the BA15s base of the 1156 has pins at the same height, so the two bayonet types are not interchangeable despite their physical similarity.
The 921 bulb is specified for the 2015-2016 model years. It is a T15 wedge bulb rated at 12V and 16W, making it the lowest-wattage bulb among the four types listed in these specifications.
The T15 socket used by the 921 and the T20 socket used by the 7440 are both wedge-type fittings, but the difference in body size means the two bulbs do not share socket compatibility.
All four bulb types in these specifications, the 1156, 1157, 7440, and 921, conform to ANSI standards applicable to the US and Canadian markets.
The 1157 specified for the 2024 model year is rated at 21W on its primary filament and 5W on its secondary filament, a dual-filament configuration that differs from every other bulb type listed in these specifications.