Mercedes-Benz E420 Back Up Light Bulb Size

The Mercedes-Benz E420 back up light requires a bulb size of P21W for the rear lighting assembly. Data for the specified component covers the range from 1994 to 1997.

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
1997	P21W
1994-1995	P21W

Bulb Specifications

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

Other Locations

Additional Notes

The P21W is the sole bulb type listed for the Mercedes-Benz E420 backup light across all specified model years, covering 1994, 1995, and 1997.
The P21W is an ECE-standard single-filament signalling bulb rated at 12 volts and 21 watts, designed primarily for signalling applications such as reverse lights.
The P21W uses a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar. The "s" designation indicates a single contact point at the base, distinguishing it from dual-contact variants.
The BA15s base type is not interchangeable with the BA15d base, which carries two contact points. Substituting a BA15d bulb in a BA15s socket would result in an improper fit.
The ECE designation on the P21W indicates compliance with United Nations Economic Commission for Europe regulations, a standard widely adopted outside North America.
At 21 watts on a 12-volt circuit, the P21W draws approximately 1.75 amperes, a figure relevant when assessing circuit load or fuse ratings in the E420's electrical system.