The Acura TSX front turn signal requires a P21/5W or 7440 bulb size, while the rear turn signal uses a 7440NA or 7440 bulb size. The replacement chart covers 2004 through 2010 model 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 7440 is the most frequently specified bulb across the Acura TSX turn signal data, appearing in both front and rear positions across the 2004-2008 model years.
The 7440 is an ANSI-standard single-filament wedge bulb in the T20 form factor, rated at 12V and 21W.
The 7440NA shares the same T20 wedge form factor, voltage, and wattage as the 7440, but its glass envelope is tinted natural amber rather than clear.
The natural amber tint of the 7440NA produces an amber signal output without relying on a colored lens, which is why it is designated for the rear turn signal position on the 2009-2010 Acura TSX.
Although the 7440 and 7440NA are physically interchangeable due to identical base and wattage, substituting a clear 7440 in a position specified for the 7440NA may affect the color output of the signal light.
The front turn signal on the Acura TSX shifted from the 7440 to the 1157 between the 2007 and 2008 model years, representing a change in both bulb type and base design.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W main filament and a 5W secondary filament, making it electrically and physically distinct from the single-filament 7440.
The dual-filament design of the 1157 allows a single bulb to serve two lighting functions, such as turn signal and parking light, within one housing.
The BAY15d bayonet base of the 1157 is not compatible with the T20 wedge socket used by the 7440 and 7440NA, so the front turn signal housings on 2009-2010 models require a different socket than those on 2004-2008 models.
The rear turn signal position uses the 7440 for 2004-2008 and transitions to the 7440NA for 2009-2010, while the bulb base and wattage remain unchanged across all those years.