BMW 740i Back Up Light Bulb Size

The BMW 740i back up light utilizes bulb sizes 921 and P21W depending on the specific version of the vehicle. Available data covers a range from 1993 through 2015 for the components listed.

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
2011-2015	921
1997-2001	P21W
1993-1995	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 740i backup light specifications reference two distinct bulb types across the listed model years: the 921 and the P21W.
The 921 is an ANSI-standard bulb, a designation governed by the American National Standards Institute and used primarily in the United States and Canada. It follows the T15 wedge form factor, operating at 12 volts and 16 watts.
The P21W is an ECE-standard bulb, regulated under the Economic Commission for Europe framework and used in European and worldwide markets. It features a BA15s bayonet base with a single filament, operating at 12 volts and 21 watts.
The BA15s bayonet base of the P21W is not interchangeable with the wedge base of the 921. The two bulb types require different socket designs, making cross-substitution incompatible without modification.
The 921 and P21W also differ in wattage, with the P21W drawing 21 watts compared to the 921 at 16 watts. Installing a higher-wattage bulb in a socket rated for a lower-wattage type can place excess load on the circuit.
The BMW 740i (2011-2015) uses the 921 bulb for the backup light position.
The P21W is specified for the 740i across the 1993-1995 and 1997-2001 model years.
The shift from P21W to 921 between the earlier and later generation 740i reflects a change in regional lighting standards adopted in the vehicle's design, consistent with North American market specifications.