Cadillac XT5 Back Up Light Bulb Size

The Cadillac XT5 back up light uses a 921 bulb size for this application. The replacement chart covers 2017 to 2020 vehicle 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.

Bulb Size by Year Range

Years	Bulb Size
2017-2020	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The Cadillac XT5 uses the 921 bulb size for the back up light across the 2017-2020 model years.
The 921 is a T15 wedge-base bulb, meaning it connects to its socket through a tapered plastic base rather than pins or a bayonet fitting.
The 921 bulb operates at 12 volts and 16 watts, which places it in the mid-range of automotive incandescent output for reverse lighting applications.
The 921 carries an ANSI designation, indicating it conforms to a standardized specification recognized in both the United States and Canada.
The T15 designation refers to the tubular shape of the bulb envelope, with the numeric portion indicating a width of 15 eighths of an inch across the glass.
Because the 921 is an ANSI-standardized wedge bulb, other bulbs sharing the T15 wedge base and the same voltage and wattage ratings are generally considered interchangeable in fitment, though confirmation against vehicle-specific socket tolerances is a factor in practice.