The Peugeot 405 brake light requires a P21/5W bulb size for proper installation and function. Data for the specified lighting component 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.
The Peugeot 405 uses two distinct bulb types across its brake lighting system for the 1989-1991 model years: the P21/5W for the standard brake lights and the P21W for the center high mount stop light.
The P21/5W is a dual-filament bulb operating at 12V with a 21W/5W output, mounted on a BAY15d bayonet base. The dual-filament design allows a single bulb to serve two functions, typically combining a lower-intensity running or tail light output with a higher-intensity brake light output.
The P21W is a single-filament bulb operating at 12V with a 21W output, mounted on a BA15s bayonet base. Its single-filament construction means it is dedicated to one lighting function only.
Both bulb types conform to ECE standards, which are recognized across Europe and internationally, reflecting the regulatory framework under which the Peugeot 405 was engineered.
The BAY15d base of the P21/5W and the BA15s base of the P21W are not interchangeable. The BAY15d base features offset locating pins to prevent incorrect single-filament bulbs from being seated in dual-filament sockets, while the BA15s base uses symmetrical pins suited only to single-filament applications.
Because the P21/5W and P21W share the same 21W primary filament rating and a similar physical profile, there is a risk of fitment confusion. The differing base configurations serve as the primary mechanical safeguard against incorrect installation.