The Mercedes-Benz S55 AMG tail light requires a P21/4W bulb size for proper installation and function. Data for the bulb specifications covers the range from 2001 to 2006.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The outer tail light positions on the Mercedes-Benz S55 AMG use the P21/4W bulb across the 2001-2006 model years.
The P21/4W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe regulatory framework used in European and worldwide automotive lighting applications.
This bulb type carries a dual-filament design, with one filament rated at 21 watts and a second rated at 4 watts, allowing a single bulb to serve two distinct lighting functions within the same housing.
The P21/4W operates on a 12-volt electrical system, which is standard for passenger vehicles of this class.
The base type for the P21/4W is the BAZ15d bayonet fitting, which is an offset twin-contact base. The offset pin arrangement is a deliberate fitment control, as it prevents incorrect installation of a single-filament bulb in a socket designed for dual-filament operation.
Because the BAZ15d base uses asymmetrically placed pins, it is not interchangeable with the more common BA15s or BA15d bayonet bases, even though the physical size of the base may appear similar at a glance.