BMW 428i Gran Coupe front turn signal bulb size PY24WNA and rear turn signal bulb size P21W are specified in this replacement chart. The chart covers 2015 to 2016 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 BMW 428i Gran Coupe uses two distinct bulb types across its front and rear turn signal positions for the 2015-2016 model years: PY24WNA at the front and P21W at the rear.
The PY24WNA follows the ANSI standard, which governs bulb specifications for the United States and Canada markets, while the P21W follows the ECE standard used in Europe and worldwide.
The front turn signal application of the PY24WNA on the BMW 428i Gran Coupe is conditional, applying only to vehicles equipped with HID headlamps.
The PY24WNA is an amber-colored variant of the ECE PY24W bulb, meaning its glass envelope is pre-tinted rather than relying on an amber lens to produce the required turn signal color.
The PY24WNA uses a PGU20-4 base, which is a specific pin-type configuration not shared with the P21W, making the two bulbs physically non-interchangeable despite their similar wattage ratings.
The PY24WNA operates at 12V and 24W, while the P21W operates at 12V and 21W, placing both within the low-voltage automotive range but at slightly different power draws.
The P21W uses a BA15s bayonet base, a single-contact configuration standard to single-filament signalling applications, distinguishing it from dual-filament bayonet bulbs that share a visually similar base style.
The designation "P21W" indicates a single-filament construction, which means the bulb serves only one lighting function per socket, consistent with a dedicated turn signal role rather than a combined stop and tail application.