BMW 128i front and rear turn signal bulbs use the 12496 and PY21W sizes respectively. The replacement chart covers 2008 to 2013 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 two bulb types specified across the BMW 128i turn signal positions are the 12496 and the PY21W. Both operate at 12 volts, making them compatible with the vehicle's standard automotive electrical system.
The PY21W is an ECE-standardized single-filament amber bulb rated at 21 watts. It uses a BAU15s bayonet base, which is an offset-pin base designed to prevent incorrect installation of non-amber bulbs in amber-designated sockets.
The 12496 is a halogen bulb designated by Philips and Osram part numbering conventions for specialty automotive applications. It is rated at 12 volts and is not an ECE-coded type in the same standardized manner as the PY21W.
The rear turn signal position on the BMW 128i uses the PY21W exclusively across all model years from 2008-2013, with no headlamp-type conditional variants listed for that position.
The front turn signal position on the BMW 128i varies by headlamp type in certain model years. In 2013 and 2010, vehicles with halogen capsule headlamps use the 12496, while those with HID headlamps use the PY21W.
In the 2012 model year, the front turn signal fitment is reversed relative to 2013 and 2010. The 12496 is specified for HID headlamp-equipped vehicles, and the PY21W is specified for halogen capsule headlamp-equipped vehicles.
The 2011 BMW 128i front turn signal carries a single PY21W specification with no headlamp-type conditional, indicating one bulb type applies regardless of headlamp configuration for that year.
The 2008 and 2009 BMW 128i front turn signal positions each specify only the 12496, also without headlamp-type conditionals.
Because the front turn signal bulb assignment between the 12496 and PY21W is not consistent across model years and headlamp configurations, substituting one for the other without confirming the specific vehicle's headlamp type risks an incorrect fitment.
The BAU15s base of the PY21W is physically distinct from standard BA15s bases. A bulb with a BA15s base cannot seat correctly in a BAU15s socket, which makes the base type a relevant factor when sourcing a replacement for any PY21W position on this vehicle.