BMW 528i Back Up Light Bulb Size

The BMW 528i back up light utilizes 921 and P21W bulb sizes for the lighting components located at the rear of the vehicle. Data for the specific bulbs covers the range from 1979 to 2016.

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
2008-2016	921
1997-2000	P21W
1979-1981	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 BMW 528i back up light specifications cover two distinct bulb types across the listed model years: the 921 and the P21W.
The 921 is an ANSI-standard wedge bulb of the T15 type, rated at 12V and 16W, and is the designated back up light bulb for the BMW 528i across the 2008-2016 model years.
The T15 designation refers to the bulb's tubular shape with a width of 15/32 of an inch, and the wedge base design means the bulb is held in place by friction rather than a locking mechanism.
The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, and it is the designated back up light bulb for the BMW 528i across the 1979-1981 and 1997-2000 model years.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet fitting, "15" refers to the 15mm base width, and "s" indicates a single contact at the base.
The 921 and P21W are not interchangeable. The 921 uses a wedge base while the P21W uses a BA15s bayonet base, making the two physically incompatible with each other's sockets.
The 921 operates at 16W while the P21W operates at 21W, representing a difference in power draw that also reflects their separate regulatory standards, ANSI and ECE respectively.
The ANSI standard governing the 921 is primarily used in the United States and Canada, while the ECE standard governing the P21W is used in Europe and other international markets.