The BMW 545i uses a 12496 PY21W bulb size for both front and rear turn signal applications, with this bulb specification representing the replacement requirement across the model line. The replacement chart covers 2004 to 2005 production years and documents the turn signal bulb sizes for this generation.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 545i uses two distinct bulb designations across its model years for turn signal applications: 12496 in 2005 and PY21W in 2004, with this change applying to both the front and rear turn signal positions.
PY21W is an ECE-standardized bulb type recognized across European and international markets, operating at 12V with a 21W output and a single filament designed specifically for amber light emission.
The BAU15s bayonet base on the PY21W is an offset-pin base, meaning it is not interchangeable with the more common BA15s straight-pin base despite a similar physical profile.
The 12496 designation is a manufacturer-specific part number used by Philips and Osram rather than a universal industry code, classifying it as a specialty halogen bulb rated at 12V.
Both the 12496 and PY21W operate on a 12V electrical system, which is standard for passenger vehicle applications in this segment.
The front and rear turn signal positions on the BMW 545i share identical bulb specifications within each model year, indicating a uniform bulb fitment across both signal locations for a given year.
Because the 12496 is a specialty halogen type identified by a proprietary part number, substitution with generic or cross-referenced bulbs carries a risk of fitment or performance incompatibility.
The PY21W's amber coloring is built into the bulb glass itself rather than produced by a colored lens, a construction method common in ECE-compliant lighting systems.