GMC S15 Jimmy Back Up Light Bulb Size

The GMC S15 Jimmy back up light utilizes 1156 and P21W bulb sizes according to the provided technical data. Information for the specified vehicle covers the period from 1983 through 1991.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1983-1991	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The GMC S15 Jimmy uses the 1156 bulb for the back up light across all listed model years, spanning 1983-1991.
The 1156 is a single-filament bulb, meaning it serves one lighting function rather than combining two, such as stop and tail, into a shared housing.
It operates on a 12-volt electrical system at 21 watts, which aligns with standard automotive low-voltage architecture.
The 1156 follows the ANSI standard, a designation recognized across both the United States and Canada, indicating a standardized specification for physical and electrical characteristics.
Its base type is BA15s, a bayonet-style mount with a single contact pin, which locks into the socket with a push-and-twist motion.
The BA15s base is not interchangeable with the BA15d base, which carries two contact pins and is used on dual-filament bulbs such as the 1157.