INFINITI QX50 front turn signal bulbs use 7440 size, while rear turn signal bulbs use 12496 or PY21W size. The replacement chart covers 2014 through 2017 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 7440 bulb is an ANSI-standard single-filament wedge bulb in the T20 form factor, rated at 12V and 21W, and is the specified front turn signal bulb for the INFINITI QX50 across the 2014-2017 model years.
The T20 wedge base of the 7440 is a push-in connector type, meaning it does not use a bayonet or screw mount, which affects physical fitment in the socket.
The rear turn signal specification for the QX50 is not uniform across the 2014-2017 range. The 2014 and 2017 model years specify the 12496, while 2015-2016 specify the PY21W.
The 12496 is a Philips/Osram proprietary part number for a 12V halogen bulb intended for specialty applications, and it is not defined by a universal ANSI or ECE standard.
The PY21W follows the ECE standard used in European and international markets. It is a single-filament amber bulb with a BAU15s bayonet base, rated at 12V and 21W.
The BAU15s base of the PY21W features an offset pin arrangement, which physically prevents it from being seated in sockets designed for the more common BA15s base, making cross-substitution mechanically incompatible without modification.
Although the 7440 and PY21W share the same voltage and wattage ratings of 12V and 21W, their base types differ entirely, and they are not interchangeable despite the matching electrical values.
The rear turn signal position on the QX50 uses two distinct bulb types across the same four-year span, meaning the correct replacement depends strictly on the specific model year rather than the position alone.