The INFINITI Q45 brake light utilizes 7443, 7440, and 1157 bulb sizes depending on the specific production period for the vehicle. Available data covers the range from 1990 through 2004.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The INFINITI Q45 brake light circuit uses three distinct bulb types across its production span: the 1157, 7440, and 7443, each sharing a 12-volt operating voltage but differing in base design and filament configuration.
The 1157 is a dual-filament bulb fitted with a BAY15d bayonet base, rated at 12V with a 21W high filament and a 5W low filament. This base type uses two offset pins at different heights to prevent incorrect installation.
The INFINITI Q45 used the 1157 for its brake lights across the 1990-1996 model years.
The 7440 is a single-filament T20 wedge bulb rated at 12V and 21W. Because it carries only one filament, it functions solely as a brake or turn signal light rather than a combined stop and tail lamp.
The 7443 is a dual-filament T20 wedge bulb rated at 12V, 21W/5W. Although it shares the T20 wedge form factor with the 7440, the two are not interchangeable in all sockets due to the 7443 carrying an additional filament contact.
The Q45 transitioned from the 7440 to the 7443 between the 2001 and 2002 model years, representing a shift from a single-filament to a dual-filament brake light configuration.
The center high mount stop light on the Q45 uses the 921 across all listed model years, from 1990-2006. The 921 is a single-filament T15 wedge bulb rated at 12V and 16W.
The T15 form factor of the 921 is physically smaller than the T20 form factor shared by the 7440 and 7443, making cross-substitution between these wedge types incompatible regardless of voltage rating.
All bulb types listed for the Q45 conform to ANSI standards applicable in the United States and Canada, indicating standardized electrical and photometric ratings across those markets.
The 1157 and 7443 both operate on a 21W/5W dual-filament arrangement, though their base types differ entirely, as the 1157 uses a bayonet mount and the 7443 uses a wedge mount, making them physically non-interchangeable.