Pontiac Firebird Back Up Light Bulb Size

The Pontiac Firebird back up light utilizes bulb sizes 1156, 1157, and P21W depending on the specific production period. Available information covers a span from 1967 through 1997.

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
1974-1997	1156
1972-1973	1157
1967-1971	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157

Other Locations

Additional Notes

The Pontiac Firebird uses the 1156 bulb for its back up light across the 1967-1974 model years, then again continuously from 1975 through 1997.
The 1156 is an ANSI-standard single-filament bulb rated at 12 volts and 21 watts, fitted with a BA15s bayonet base.
The BA15s bayonet base features a single contact pin, which corresponds directly to the single-filament design of the 1156.
The 1972-1973 Pontiac Firebird departs from the otherwise uniform fitment by specifying the 1157 bulb for the back up light.
The 1157 is an ANSI-standard dual-filament bulb rated at 12 volts with a 21W/5W output, fitted with a BAY15d bayonet base.
The BAY15d base used by the 1157 carries two offset contact pins to support its dual-filament configuration, making it physically distinct from the BA15s base of the 1156.
Because the 1156 and 1157 use different bayonet base configurations, the two bulb types are not interchangeable despite sharing the same 12-volt operating voltage.
Both the 1156 and 1157 conform to ANSI standards recognized in the United States and Canada.