INFINITI Q45 Back Up Light Bulb Size

The INFINITI Q45 back up light utilizes bulb sizes 921, 7440, 1156, and P21W depending on the specific version of the vehicle. Available data covers a range from 1990 through 2006 for the components listed.

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
1999-2006	921
1997-1998	7440
1990-1996	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The INFINITI Q45 backup light bulb specifications span model years 1990 through 2006, with three distinct bulb types used across that range: the 921, 7440, and 1156.
The 921 bulb is the most frequently specified type, covering the Q45 from 1999 to 2006. It is a T15 wedge bulb rated at 12V and 16W, conforming to ANSI standards for the US and Canadian markets.
The 1156 bulb is the second most frequently specified type, used in the Q45 from 1990 to 1995. It operates at 12V and 21W, and uses a BA15s bayonet base rather than a wedge-style connection.
The 7440 bulb is specified for the 1997-1998 Q45. It is a T20 single-filament wedge bulb rated at 12V and 21W, and like the 1156, it carries a higher wattage than the 921.
Although the 1156 and 7440 share the same 12V, 21W electrical rating, their base types are not interchangeable. The 1156 uses a BA15s bayonet base, while the 7440 uses a T20 wedge base, making physical fitment incompatible between the two.
The 921 wedge base and the 7440 wedge base are both wedge-style connections, but they differ in size. The T15 socket of the 921 and the T20 socket of the 7440 are not the same, and substituting one for the other is not supported by the specifications.
The transition from the 1156 bayonet-base bulb to the 7440 wedge-base bulb between the 1995 and 1997 Q45 represents a change in both base type and connection style, which affects socket compatibility.
The subsequent transition from the 7440 to the 921 between the 1998 and 1999 Q45 involves a reduction in wattage from 21W to 16W, as well as a change from a T20 to a T15 wedge base.