BMW 335i Back Up Light Bulb Size

The BMW 335i back up light requires a bulb size of P21W for the rear lighting assembly. Data for the specified component covers the range from 2014 to 2015.

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
2014-2015	P21W

Bulb Specifications

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

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Additional Notes

The P21W is the specified back up light bulb for the BMW 335i across the 2014-2015 model years.
The P21W follows the ECE (Economic Commission for Europe) standard, a regulatory framework used across Europe and numerous other markets worldwide.
This bulb operates on a 12-volt electrical system, which is the standard voltage architecture found in passenger vehicles.
At 21 watts, the P21W falls within the single-filament signalling category, meaning it produces one fixed output level with no high or low beam switching capability.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet-style mount, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
The BA15s single-contact base is distinct from the BA15d double-contact variant; substituting one for the other is not compatible due to differing electrical contact configurations.