The BMW 135i uses PY21W bulbs with 12496 designation for both front and rear turn signal applications, with bulb size specifications detailed for the vehicle. The replacement chart covers 2008 through 2013 model years and documents turn signal bulb specifications across the production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 135i turn signal system uses two bulb types across its production run: the PY21W and the 12496, both rated at 12 volts.
The PY21W is an ECE-standard single-filament amber bulb operating at 21 watts, fitted with a BAU15s bayonet base, a base type that uses an offset pin arrangement to prevent incorrect installation of non-amber bulbs.
The 12496 is a Philips/Osram part number designation for a halogen bulb intended for specialty automotive applications, also rated at 12 volts.
For the 2009-2010 BMW 135i, the front turn signal bulb type is determined by the headlamp configuration: the 12496 is specified for vehicles with halogen capsule headlamps, while the PY21W is specified for vehicles with HID headlamps.
The 2008 BMW 135i front turn signal reverses this pairing relative to the 2009-2010 model years, with the PY21W fitted to halogen capsule headlamp vehicles and the 12496 fitted to HID headlamp vehicles.
Because the front turn signal bulb assignment is headlamp-dependent in 2008-2010 model years, confirming the installed headlamp type is necessary before selecting a replacement bulb for those vehicles.
The 2013 BMW 135i front turn signal uses the PY21W, while the rear turn signal for the same year uses the 12496, meaning the front and rear positions on that model year do not share a common bulb type.
The 2012 BMW 135i presents the inverse arrangement, with the 12496 at the front and the PY21W at the rear, again requiring separate bulb types for the two positions.
For the 2009-2011 rear turn signal, the 12496 is specified across all three years without any conditional headlamp-based variation.
The BAU15s base of the PY21W is not interchangeable with the more common BA15s base found on standard single-filament bulbs, as the offset pin spacing differs between the two base types.