BMW 325i Back Up Light Bulb Size

The BMW 325i back up light requires a P21W bulb size for proper installation and function within the rear lighting assembly. Available data for the specified bulb covers the range from 1988 through 2006.

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
2001-2006	P21W
1993-1995	P21W
1988-1991	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 BMW 325i uses the P21W bulb as the specified back up light bulb across all listed model years.
The P21W is an ECE-standard bulb, meaning it conforms to European and internationally recognized automotive lighting regulations.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is typical for single-filament incandescent signalling applications.
The P21W uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin offset on the base collar.
Because the BA15s base is a single-contact design, it is not interchangeable with the BA15d base, which carries two contacts for dual-filament bulbs.
The single-filament construction of the P21W means it serves one lighting function only, which is consistent with its use in a dedicated back up light position.
The BMW 325i (2001-2006) carries the same P21W specification as the earlier listed model years, indicating a consistent fitment across generations of this model.
The P21W designation follows the IEC/ECE naming convention, where "P" refers to the bulb's prefocus cap type and "21W" denotes the wattage rating.