The Geo Metro brake light utilizes 1157 and 1156 bulb sizes for the rear lighting system components. Available information covers the span of time from 1989 through 1997 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 Geo Metro uses three distinct bulb types across its brake lighting system: the 1157, the 1156, and the 921, each serving specific positions and model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output. Its two filaments allow it to serve both a steady brake function and a lower-intensity running light function within a single housing.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. Although its base shares the same 15mm bayonet collar width as the 1157, the single-filament design and differing pin offset make the two types non-interchangeable.
The 921 is a wedge-base bulb of the T15 type, rated at 12V and 16W. Unlike the bayonet-base 1157 and 1156, it is held in place by the tension of its socket rather than a twist-lock mechanism.
For the Geo Metro, the 1157 is the most widely specified brake bulb, covering the standard brake light position across 1989-1991 and 1993-1997.
The 1992 Geo Metro is the only model year in the specifications where the 1156 is used in the standard brake light position rather than the 1157, representing a fitment difference that warrants attention when sourcing a replacement.
The center high mount stop light on the 1992-1994 Geo Metro uses the 1156, while the same position on the 1993-1997 Metro transitions to the 921. The 1992 year falls under the 1156 specification for both the standard brake and center high mount positions.
Because the BAY15d base of the 1157 and the BA15s base of the 1156 differ in their pin configurations, substituting one for the other is not physically possible without modifying the socket, making year-specific fitment verification necessary for the Metro.
The 921 wedge bulb used in the center high mount stop light position from 1993-1997 operates at a lower wattage than the 1156 it replaced in earlier Metro years, reflecting a difference in the lamp assembly design between those production periods.
All three bulb types specified for the Geo Metro, the 1157, 1156, and 921, conform to ANSI standards recognized in both the United States and Canada.