Saab 9-3 Back Up Light Bulb Size

The Saab 9-3 back up light utilizes 921 and P21W bulb sizes depending on the specific version of the vehicle. Available data for the lighting components covers the range from 1999 through 2011.

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
2008-2011	921
1999-2007	P21W

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The Saab 9-3 backup light specification covers model years 1999-2011 and references two distinct bulb types across that span: the 921 and the P21W.
The 921 is an ANSI-standard wedge bulb of the T15 form factor, rated at 12V and 16W, and is the designated backup light bulb for the 2008-2011 Saab 9-3.
The P21W follows the ECE standard used in Europe and worldwide markets, features a BA15s single-contact bayonet base, and is rated at 12V and 21W. It is specified for the 1999-2007 Saab 9-3.
The two bulb types are not interchangeable. The 921 uses a wedge base, while the P21W uses a BA15s bayonet base, meaning the socket design differs between the two production periods.
The P21W operates at 21W, which is 5W higher than the 921 at 16W. Both run on a 12V system, but the wattage difference reflects a distinction in light output between the two standards.
The shift from P21W to the 921 in the 2008 Saab 9-3 corresponds to a change from an ECE-standard component to an ANSI-standard one, which is consistent with market-specific regulatory differences between North American and European vehicle configurations.
The BA15s designation on the P21W indicates a single-contact bayonet cap with a 15mm base width, a base type common in European automotive lighting applications.