Porsche Cayenne Back Up Light Bulb Size

The Porsche Cayenne back up light utilizes a P21W bulb size for illumination. Data for the specified component covers the range from 2003 through 2010.

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
2008-2010	P21W
2003-2006	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 sole backup light bulb type listed across all specified model years of the Porsche Cayenne, covering 2003-2006 and 2008-2010.
The P21W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe's lighting regulations, which are widely adopted outside North America.
As a single-filament bulb, the P21W is dedicated to one lighting function, which in this application is the backup light circuit.
The P21W operates at 12 volts and consumes 21 watts, placing it in the standard low-voltage automotive range typical of passenger vehicle electrical systems.
The P21W uses a BA15s bayonet base, where "BA15" refers to the 15mm base width and "s" denotes a single contact pin, distinguishing it from dual-contact variants.
The BA15s single-contact base is not interchangeable with the BA15d base, which carries two offset pins for dual-filament bulbs. Substituting one for the other is not possible without a socket modification.
The Porsche Cayenne (2003-2006 and 2008-2010) backup light sockets are designed specifically for the BA15s fitment, so any replacement bulb must match that base configuration to seat correctly.
The P21W designation follows an international naming convention where "P" indicates a prefocus-style lamp body and "21W" reflects the wattage rating.