The GMC S15 front and rear turn signal bulbs both utilize a 2057 size bulb for proper operation. The replacement chart covers vehicle production spanning 1982 to 1990.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC S15 uses the 2057 bulb for both the front and rear turn signals across all model years covered in the specifications, spanning 1982-1990.
The 2057 is a dual-filament bulb, meaning it contains two separate filaments within a single housing, allowing it to serve more than one lighting function at different wattage levels.
The 2057 operates on a 12-volt electrical system and draws 26.9 watts on its high-intensity filament and 8 watts on its low-intensity filament.
The 2057 uses a BAY15d bayonet base, which is an offset twin-pin base design. The offset pin placement is a physical keying feature that controls insertion orientation.
The 2057 is classified as an ANSI standard bulb applicable in both the United States and Canada.
The 2057 is a brighter variant of the 1157 bulb. While the two share the same BAY15d base and are physically interchangeable in many sockets, the 2057 produces greater output on its high-intensity filament.
Because the 1157 and 2057 share the same base type, an 1157 may fit the S15 socket physically, though it would operate at a lower wattage than the specified 2057 on the high-intensity filament.