Cadillac CT6 Turn Signal Bulb Size

The Cadillac CT6 rear turn signal requires a 921 bulb size for proper illumination. The replacement chart covers 2016 to 2018 production years with corresponding bulb specifications.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Rear Turn Signal

Years	Bulb Size
2016-2018	921

Bulb Specifications

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

Other Locations

Additional Notes

The 921 bulb is the specified rear turn signal size for the Cadillac CT6 across the 2016-2018 model years.
The 921 is classified as a T15 wedge-base bulb, meaning it uses a plastic wedge at its base rather than a metal pin or bayonet fitting to secure itself within the socket.
The 921 operates at 12 volts and 16 watts, which places it within the standard low-voltage electrical architecture common to passenger vehicles.
The 921 carries ANSI standardization recognized in both the United States and Canada, indicating the bulb conforms to a defined set of performance and construction criteria shared across those markets.
The T15 designation refers to the tubular envelope size of the bulb, with the numeric portion representing the width in eighths of an inch, making the envelope approximately 15 eighths of an inch wide.
Wedge-base bulbs such as the 921 are not interchangeable with bayonet-base or pin-base bulb types, as the socket design is specific to the base configuration.