The INFINITI QX4 front turn signal uses a 7440, 1156NA, or 1156 bulb size, while the rear turn signal requires a 1156NA or 1156 bulb size. The replacement chart covers vehicle production years spanning 1997 to 2003 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 INFINITI QX4 turn signal specifications cover model years 1997 through 2003 across both front and rear positions.
Three bulb types appear across these specifications: the 7440, the 1156NA, and the 1156. All three are ANSI-standard single-filament bulbs rated at 12V and 21W.
The 7440 is a T20 wedge-base bulb, meaning it uses a plastic wedge to secure into its socket rather than a bayonet-style base. It is specified for the front turn signal on the INFINITI QX4 for model years 2001-2003.
The 1156 and 1156NA both use a BA15s bayonet base, which features a single pin and requires a push-and-twist motion to seat into the socket. This base type is distinct from the wedge fitting used by the 7440.
The 1156NA is a natural amber glass variant of the 1156. The amber tint is built into the glass envelope itself rather than produced by a clear bulb inside a colored lens.
Because the 7440 and the 1156-series bulbs use physically different base types, they are not interchangeable with one another regardless of their matching voltage and wattage ratings.
The front turn signal position transitioned from the 1156 (1997-1998) to the 1156NA (1999-2000) and then to the 7440 (2001-2003), reflecting three distinct bulb specifications across the production run of this position alone.
The rear turn signal on the QX4 used the 1156 for 1997-1998 and the 1156NA for 1999-2003. Since both share the BA15s bayonet base, the physical socket remained compatible across those years, with the amber glass coating being the differentiating factor.
For 1999-2000 model years, the front and rear turn signals share the same 1156NA specification, while the 2001-2003 front position diverges to the 7440, making year verification necessary before sourcing a front bulb for those later models.
The 1156NA is the most frequently specified bulb across the full set of turn signal positions and years on the QX4, appearing in both front and rear applications across multiple model years.