Peugeot 405 Back Up Light Bulb Size

The Peugeot 405 back up light requires a bulb with the specific P21W size for proper installation. Data for the bulb size covers the range from 1989 to 1991.

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
1989-1991	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 P21W is the sole bulb type listed for the Peugeot 405 back up light across the 1989-1991 model years.
The P21W is governed by ECE (Economic Commission for Europe) standards, which are recognized across Europe and numerous other markets worldwide.
The P21W operates on a 12-volt electrical system and draws 21 watts, which is typical for single-filament incandescent signalling applications.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet-type fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
As a single-filament bulb, the P21W serves one dedicated function per housing, which is consistent with its use in a back up light application.
The BA15s base is not interchangeable with the BA15d base, which carries two contacts. Substituting a dual-contact bulb in a single-contact socket would result in an improper fit.