GMC C15 Suburban Back Up Light Bulb Size

The GMC C15 Suburban back up light bulb size specifications include 199 and 1156 bulb options for this vehicle model. The replacement chart covers 1973 through 1978 production years with corresponding bulb size data.

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
1977-1978	199
1975-1976	1156
1974	199
1973	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	199
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The GMC C15 Suburban backup light specifications cover model years 1973-1978, with two bulb types used across this range: the 199 and the 1156.
Both the 199 and 1156 are ANSI-standardized bulbs recognized in the United States and Canada, each operating at 12 volts and 21 watts with a single filament.
Both bulb types share the BA15s bayonet base, a single-contact base design that secures the bulb with a twist-lock mechanism.
The 199 is a variant of the 1156, meaning the two share the same base type, voltage, wattage, and filament configuration.
The GMC C15 Suburban used the 1156 in model years 1973, 1975, and 1976, and the 199 in model years 1974, 1977, and 1978.
Because the 199 and 1156 share identical electrical and base specifications, the two bulbs are functionally interchangeable in backup light applications.