Cadillac CT6 Back Up Light Bulb Size

The Cadillac CT6 back up light uses a 921 bulb size for the rear illumination system. Data for the specific component covers the range from 2016 to 2020.

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
2016-2020	921

Bulb Specifications

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

Other Locations

Additional Notes

The Cadillac CT6 uses the 921 bulb size for the back up light across the 2016-2020 model years.
The 921 is a T15 wedge-base bulb, meaning it connects to its socket through a tapered plastic base rather than metal pins or a bayonet fitting.
The 921 operates at 12 volts and 16 watts, which is consistent with standard automotive electrical systems.
The 921 bulb carries 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, with the numeric portion indicating the width in eighths of an inch.
The wedge base design of the 921 makes it non-interchangeable with bayonet-style or pin-base bulbs, even when voltage and wattage ratings are similar.