The Mercedes-Benz ML500 tail light requires a P21/4W bulb size for the rear lighting assembly. Provided information covers the specific time period from 2002 through 2007.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21/4W is the most frequently specified bulb across the Mercedes-Benz ML500 tail light data, appearing in both outer tail light positions across the 2002-2007 model years, with the exception of the outer tail light position in 2006 and 2007, where the P21W is specified instead.
The P21/4W operates on a dual-filament design rated at 12V with two wattage outputs: 21W for the brighter filament and 4W for the dimmer filament, making it suitable for functions that require two distinct brightness levels within a single bulb.
The P21W is a single-filament bulb rated at 12V and 21W, intended for signalling functions that require only one brightness level rather than a combined stop and tail function.
A critical fitment distinction exists between the P21W and P21/4W: the P21W uses a BA15s bayonet base with a single contact pin, while the P21/4W uses a BAZ15d bayonet base with offset dual contact pins. These two bases are not interchangeable despite the bulbs sharing a similar physical profile.
The BAZ15d base of the P21/4W features asymmetrically placed pins, a design that prevents incorrect installation by ensuring the bulb can only be seated in one orientation, which is necessary for correct filament-to-circuit alignment.
Both the P21W and P21/4W conform to ECE regulations, a lighting standard recognized across Europe and numerous other markets worldwide.
For the Mercedes-Benz ML500, the outer tail light position used the P21/4W from 2002-2005, then transitioned to the P21W in 2006-2007, indicating a change in the bulb specification for that specific position across the production run.
The second outer tail light position across all listed years, 2002-2007, consistently specifies the P21/4W, with no variation in bulb type across that span.