The Scion xA back up light requires a bulb size of 921 for proper installation and function within the rear lighting assembly. Data for the specified component covers the range from 2004 through 2006.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 921 is an ANSI-standardized bulb used in both the United States and Canada, operating at 12 volts with a power draw of 16 watts.
The 921 follows a T15 wedge base design, meaning it uses a tapering plastic base that presses directly into a socket without a separate metal base or locking mechanism.
The Scion xA uses the 921 bulb across all back up light positions for the 2004-2006 model years, covering both the general back up light and the outer back up light sub-position.
Because the general back up light and the outer back up light share the same 921 specification across the 2004-2006 model years, the same bulb type fits both positions on the Scion xA.
The T15 wedge form factor is a common automotive standard, and several bulbs share this base type. However, wattage ratings differ between them, and substituting a bulb with a different wattage than the specified 16 watts may affect socket compatibility or circuit load.