The Lexus LS400 brake light utilizes 1157 and 7443 bulb sizes for the various lighting components. Available data covers the range from 1990 through 2000 for the specified vehicle.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lexus LS400 uses two distinct bulb types across its production run for the brake light position: the 7443 for model years 1995-2000 and the 1157 for model years 1990-1994.
The 7443 is a dual-filament wedge bulb in the T20 form factor, rated at 12V with a 21W high filament and a 5W low filament, conforming to ANSI standards applicable in the US and Canada.
The 1157 is also a dual-filament bulb rated at 12V with the same 21W/5W output as the 7443, but it uses a BAY15d bayonet base rather than a wedge-style fitting, making the two types physically incompatible despite sharing identical wattage ratings.
Because the 7443 and 1157 differ in base type, a wedge socket and a bayonet socket are not interchangeable, and substituting one bulb for the other in the brake light position is not possible without a socket adapter or wiring modification.
The center high mount stop light on the Lexus LS400 uses the 921 bulb across all model years from 1990-2000, representing the only position with no change in bulb specification throughout the vehicle's entire production span covered by these data.
The 921 is a single-filament wedge bulb in the T15 form factor, rated at 12V and 16W, conforming to ANSI standards for the US and Canadian markets.
The T15 form factor of the 921 is physically smaller than the T20 form factor of the 7443, and the two wedge bulbs are not interchangeable despite both using a wedge-style base.
Both the 7443 and the 1157 share a dual-filament design, which in a brake light application typically serves a combined stop and tail light function through the two separate filaments.