BMW M6 Back Up Light Bulb Size

The BMW M6 back up light utilizes 921 and P21W bulb sizes for the rear illumination system. Available data for the specified vehicle covers the time range from 1987 through 2018.

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
2012-2018	921
2006-2010	P21W
1987-1988	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 M6 backup 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 (T15) rated at 12V and 16W, a format primarily used in North American markets.
The P21W follows the ECE standard, which governs lighting regulations in Europe and much of the rest of the world. It uses a BA15s single-contact bayonet base and is rated at 12V and 21W.
The BA15s bayonet base of the P21W is not interchangeable with the wedge-style socket of the 921, meaning the two bulb types serve physically incompatible housings.
The P21W operates at 21W compared to the 921's 16W, reflecting a difference in power draw that also corresponds to the differing regulatory standards each bulb was designed to meet.
The BMW M6 (2012-2018) uses the 921 bulb for the backup light position.
The 2006-2010 model years, along with the 1987 and 1988 model years, use the P21W in the same position.
The T15 designation of the 921 refers to its wedge base form factor, in which the glass envelope itself acts as the retention mechanism within the socket, requiring no separate base hardware.