Mazda CX-9 Back Up Light Bulb Size

The Mazda CX-9 back up light utilizes 921 and 7440 bulb sizes depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 2007 to 2023.

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
2019-2023	921
2013-2017	921
2007-2012	7440

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440

Other Locations

Additional Notes

The Mazda CX-9 backup light uses one of two bulb types across its model years: the 921 (T15 wedge) for 2013-2023 and the 7440 (T20 wedge) for 2007-2012.
The 921 is a T15 wedge bulb rated at 12V and 16W, standardized under ANSI specifications for the US and Canadian markets.
The 7440 is a T20 single-filament wedge bulb rated at 12V and 21W, also conforming to ANSI standards for the US and Canadian markets.
Although both the 921 and 7440 are wedge-type bulbs operating at 12V, they are not interchangeable. The T15 and T20 designations indicate different physical sizes, and the wattage differs by 5W between the two types.
The single-filament designation of the 7440 confirms it serves only one lighting function, which is consistent with its application as a dedicated backup light in the Mazda CX-9 (2007-2012).
A bulb type change occurred between the 2012 and 2013 model years of the CX-9, shifting from the higher-wattage 7440 to the lower-wattage 921.