Mercedes-Benz ML430 front side marker bulbs utilize a 1157NA size while rear side marker bulbs require a P21/4W size. The replacement chart covers 1999 to 2001 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz ML430 uses two distinct bulb types across its front and rear side marker positions, with the 1157NA fitted at the front and the P21/4W fitted at the rear for the 1999-2001 model years.
The 1157NA is a dual-filament bulb operating at 12V with a 21W main filament and a 5W secondary filament, housed in natural amber glass with a BAY15d bayonet base, and it conforms to ANSI standards used in the United States and Canada.
The P21/4W is also a dual-filament signalling bulb rated at 12V, with a 21W main filament and a 4W secondary filament, and it conforms to ECE standards used in Europe and internationally.
Although both the 1157NA and P21/4W share a dual-filament design and similar wattage ratings, they are not interchangeable due to their different base types: the 1157NA uses a BAY15d base while the P21/4W uses a BAZ15d base.
The BAY15d and BAZ15d bases differ in the offset positioning of their locating pins, which physically prevents cross-fitment between the two bulb types.
The natural amber glass of the 1157NA produces a filtered amber output directly from the bulb, whereas the P21/4W relies on the vehicle's lens housing to produce the required color output.
The secondary filament wattage differs between the two bulb types, with the 1157NA rated at 5W and the P21/4W rated at 4W, reflecting the differing power draw expectations under their respective regulatory standards.