BMW 320i Back Up Light Bulb Size

The BMW 320i back up light utilizes H21W and P21W bulb sizes for the rear illumination system. Available information covers the time range from 1977 through 2018 for the specified vehicle.

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
2016-2018	H21W
2013-2015	P21W
1977-1983	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BAY9s base. 12V, 21W.	H21W
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

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Additional Notes

The two bulb types specified for the BMW 320i backup light are the H21W and the P21W, both of which are ECE-rated single-filament signalling bulbs operating at 12 volts and 21 watts.
Despite sharing identical voltage and wattage ratings, the H21W and P21W are not interchangeable, as each uses a distinct base type.
The H21W uses a BAY9s base, which features offset pins to ensure correct orientation during installation.
The P21W uses a BA15s bayonet base, a single-contact design with symmetrically placed pins.
The BMW 320i (2016-2018) takes the H21W bulb for the backup light position.
The P21W is specified for the 2013-2015 model years, representing a different base type from the H21W used in the immediately following years.
The P21W is also specified for the 1977-1983 model years, making it the bulb type associated with the earliest generation covered in these specifications.
Both the H21W and P21W conform to ECE standards, meaning they are recognized for use in European and worldwide automotive lighting applications.