The Toyota Supra back up light utilizes 7440, P21W, and 1156 bulb sizes depending on the specific version of the vehicle. Information provided covers the range from 1986 through 1998.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1156 bulb is a single-filament type with a BA15s bayonet base, rated at 12V and 21W under the ANSI standard applicable to the US and Canada. The BA15s designation refers to a single-contact bayonet cap with a 15mm base width.
The 7440 bulb is a single-filament wedge type in the T20 form factor, also rated at 12V and 21W under the same ANSI standard. The T20 designation refers to a wedge-style base rather than a bayonet fitting, making the two bulb types physically incompatible with each other despite sharing identical voltage and wattage ratings.
The Toyota Supra used the 1156 bulb for its back up light across the 1986-1995 model years, representing the longer-running fitment of the two bulb types found in these specifications.
The 7440 replaced the 1156 as the back up light bulb for the 1997-1998 Supra, reflecting a base-type change that makes earlier and later bulbs non-interchangeable.
The 1996 Supra back up light specifications include a mid-year production change. Units produced through July 1996 used the 1156, while those produced from July 1996 onward used the 7440, meaning two different bulb types apply to the same model year depending on production date.
The Outer Back Up Light on the 1998 Supra carries a production cutoff notation of "To 08/1998," indicating the 7440 fitment applies only to units built before that date within the model year.
Both the 1156 and 7440 operate at the same 12V, 21W output, so their light output is equivalent. The difference lies solely in the base type, which determines physical fitment into the socket.
Because the 1156 uses a bayonet base and the 7440 uses a wedge base, substituting one for the other is not possible without a socket adapter, regardless of their matching electrical ratings.