Porsche Carrera GT Back Up Light Bulb Size

The Porsche Carrera GT back up light requires a P21W bulb size for the rear lighting assembly. Data for the specified vehicle covers the range from 2004 to 2005.

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
2004-2005	P21W

Bulb Specifications

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

Other Locations

Additional Notes

The P21W is the specified back up light bulb for the Porsche Carrera GT across its 2004-2005 production run.
The P21W operates on a 12-volt electrical system and draws 21 watts, which is standard 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, making it distinct from dual-filament types that serve two lighting roles from one housing.
The P21W is governed by ECE regulations, a lighting standard recognized across Europe and numerous markets worldwide, ensuring consistent performance and interchangeability within that specification.
The BA15s base of the P21W is not interchangeable with the BA15d base, which carries two offset pins. Substituting a BA15d bulb in a BA15s socket is not possible without modification.