BMW 740iL Back Up Light Bulb Size

The BMW 740iL back up light requires a P21W bulb size for proper installation and function within the rear lighting assembly. Available data covers the production range from 1993 through 2001.

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
1993-2001	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 740iL uses the P21W bulb size for the back up light across the 1993-2001 model years.
The P21W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe's regulations, which govern lighting equipment used in Europe and many other markets worldwide.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is a standard wattage for single-filament signalling applications.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
Because the P21W is a single-filament bulb, it serves one dedicated function per housing, in this case the reverse light, rather than combining multiple functions such as brake and tail into one unit.
The BA15s bayonet base is not interchangeable with dual-contact bayonet bases such as the BA15d, as the contact configuration differs and substitution would result in incorrect fitment.