GMC Typhoon Back Up Light Bulb Size

The GMC Typhoon back up light requires bulb size 1156 or P21W depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 1992 to 1993.

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
1992-1993	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 1156 is the sole bulb type listed for the GMC Typhoon backup light across both model years covered in the specifications, 1992-1993.
The 1156 operates on a 12-volt electrical system and draws 21 watts, placing it in the standard incandescent range for single-circuit automotive lighting applications.
As a single-filament bulb, the 1156 serves one dedicated function per socket, which aligns with its role in a backup light application where only one lighting state is required.
The 1156 uses a BA15s bayonet base, a mount type in which a single pin on the bulb base locks into the socket with a push-and-twist motion, distinguishing it from the dual-pin BA15d base used on some other automotive bulbs.
The 1156 carries ANSI standardization recognized in both the United States and Canada, meaning the bulb conforms to a defined set of electrical and physical tolerances rather than being a proprietary specification.
Because the BA15s base is a single-contact design, it is not interchangeable with dual-contact bayonet bulbs such as the 1157, even though those bulbs share a visually similar base profile.