Lexus LS400 front and rear side marker bulbs utilize 168 and 194 sizes for front applications, with 168 and 1157 sizes for rear positions. The replacement chart covers 1990 through 2000 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lexus LS400 uses three distinct bulb types across its side marker positions: the 168, 194, and 1157, each carrying ANSI standardization for the US and Canadian markets.
The 168 and 194 are both T10 miniature wedge bulbs operating at 12V, though they differ in wattage. The 168 draws 4.9W, while the 194 draws 3.78W, making them physically similar but not electrically identical.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output. Its bayonet base and dual-filament design make it physically and electrically incompatible with the T10 wedge sockets used by the 168 and 194.
For the front side marker on the Lexus LS400, the 1998-2000 model years use the 168 bulb, while the 1990-1997 model years use the 194 bulb.
Although the 168 and 194 share the same T10 wedge form factor, the wattage difference between them represents a meaningful distinction in socket load, and the two are not considered direct substitutes in applications where wattage tolerance is a factor.
The rear side marker on the LS400 shifted from the 1157 bayonet-base bulb used in 1990-1994 to the 168 T10 wedge bulb starting in 1995, a change that reflects a difference in socket type between those production periods.
The 1157's dual-filament design, with separate 21W and 5W circuits, is a characteristic typically associated with combined stop and tail light functions, which distinguishes it from the single-filament 168 and 194 used elsewhere on the LS400.
The front and rear side markers on the 1998-2000 LS400 both use the 168 bulb, meaning the same bulb type serves both positions across those model years.
For the 1990-1994 LS400, the front and rear side markers use different bulb types, with the 194 at the front and the 1157 at the rear, requiring separate bulb stock for those positions.