Pontiac G8 Back Up Light Bulb Size

The Pontiac G8 back up light requires a bulb size of P21W for the rear lighting assembly. Data for the specified component covers the range from 2008 to 2009.

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
2008-2009	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

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Additional Notes

The P21W is the specified back up light bulb for the Pontiac G8 across its full production run of 2008-2009.
The P21W follows the ECE (Economic Commission for Europe) standard, a regulatory framework used across Europe and numerous other markets worldwide.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is typical for single-filament automotive signalling applications.
The P21W uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin offset to one side of the base.
As a single-filament bulb, the P21W is dedicated to one function only, which in this application is the reverse light.
The BA15s base is not interchangeable with the BA15d (dual-contact) bayonet base, and substituting one for the other is not possible without modification.