BMW 530i Back Up Light Bulb Size

The BMW 530i back up light utilizes H21W, 921, and P21W bulb sizes depending on the specific production period for the vehicle. Available data covers the range from 1975 through 2020.

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
2018-2020	H21W
2004-2007	921
2001-2003	P21W
1994-1995	P21W
1975-1978	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BAY9s base. 12V, 21W.	H21W
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 530i backup light specifications reference three distinct bulb types across its model years: H21W, 921, and P21W.
The H21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, fitted with a BAY9s base. The BAY9s is a bayonet-style base with offset pins, which prevents accidental substitution with physically similar bulbs that use different base configurations.
The P21W is also an ECE-standard single-filament signalling bulb rated at 12V and 21W, but it uses a BA15s bayonet base rather than the BAY9s found on the H21W. Despite sharing the same voltage and wattage, the two bulbs are not interchangeable due to their differing base types.
The 921 follows the ANSI standard used in the United States and Canada. It is a T15 wedge bulb rated at 12V and 16W, making it the lowest-wattage option among the three types listed in these specifications.
The BMW 530i (2018-2020) uses the H21W bulb for the backup light position.
The 921 wedge bulb was specified for the 2004-2007 model years. Its wedge base design requires no separate socket locking mechanism, as the bulb is held in place by tension from the housing contacts.
The P21W was specified across the widest span of model years in these specifications, covering 1975-1978, 2001-2003.
The H21W and P21W share the same 12V, 21W electrical rating, but their base types are mechanically incompatible with each other, meaning a socket designed for one will not physically accept the other.
The ECE standard governs bulb specifications primarily in European and worldwide markets, while the ANSI standard applies to North American markets. The presence of both standards across different model years of the same vehicle reflects regional variation in parts sourcing or market-specific assembly.
The shift from the P21W to the 921 between the 2003 and 2004 model years represents a change from an ECE-standard bayonet base bulb to an ANSI-standard wedge base bulb, with a corresponding reduction in wattage from 21W to 16W.