BMW 230i front turn signal uses 12496 bulb size while rear turn signal requires 7440 bulb size for replacement. The chart covers 2017 to 2020 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 230i uses different front turn signal bulb sizes across model years, with the 2017 model year specifying a PY21W bulb and the 2018 model year specifying a 12496 bulb.
The PY21W is an ECE-standard single-filament amber bulb rated at 12V and 21W, fitted with a BAU15s bayonet base. Its amber coloring is built into the bulb itself rather than relying on a colored lens.
The 12496 is a Philips/Osram part number designating a halogen bulb for specialty applications, rated at 12V. It is identified by a manufacturer-specific designation rather than a universal standard code.
The rear turn signal on the BMW 230i also varies by model year. The 2017-2018 model years use a P21W bulb, while the 2019-2020 model years use a 7440 bulb.
The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base. The BA15s base differs from the BAU15s base of the PY21W in that its pins are symmetrically positioned, making the two bases physically incompatible with each other.
The 7440 is an ANSI-standard single-filament wedge bulb of the T20 form factor, rated at 12V and 21W. It is the North American market equivalent in wattage to the ECE P21W but uses a wedge base rather than a bayonet fitting, making the two non-interchangeable.
The shift from P21W to 7440 in the rear turn signal between the 2018 and 2019 model years reflects a base-type change from bayonet to wedge, and substituting one for the other without an adapter would result in an incorrect fit.