The Lexus LS400 back up light utilizes 7440, 1156, and P21W bulb sizes depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 1990 through 2000.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lexus LS400 back up light specifications cover the full production run of the model, spanning 1990-2000.
Two bulb types appear across these specifications: the 7440 and the 1156. Both are ANSI-standard bulbs rated at 12V and 21W, making them identical in voltage and wattage despite differing in base type.
The 7440 is a single-filament wedge bulb in the T20 form factor, meaning it is retained in the socket by the wedge shape of its base rather than by a locking mechanism.
The 1156 uses a BA15s bayonet base, a single-contact bayonet fitting that locks into the socket with a twist. It is not interchangeable with the 7440 due to the difference in base design.
The Lexus LS400 back up light used the 1156 bulb for model years 1990-1994, then transitioned to the 7440 for 1995-2000. Substituting one for the other without an adapter is not possible given the incompatible base types.
The Inner Back Up Light position is specified separately for 1995-2000, and it uses the 7440 bulb across all listed years for that position.
The 1995 Inner Back Up Light entry carries a "From 10/1994" qualifier, indicating a mid-production-year introduction of that light position rather than a change at the start of the model year.
For 1995-2000, both the standard back up light and the Inner Back Up Light share the same 7440 bulb specification, meaning the same bulb type serves both positions in those years.