Cadillac XT4 Back Up Light Bulb Size

The Cadillac XT4 back up light requires a bulb size of 7440 for the rear exterior lighting system. Data for the specific bulb requirements covers the range from 2021 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	US Type	EU Type	Shop
2023	7440	W21W	Check Price
2021	7440	W21W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440	Check Price

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Additional Notes

The 7440 is an ANSI-standardized bulb type recognized across the United States and Canada, which means it follows a defined set of electrical and physical parameters rather than varying by manufacturer interpretation.
The 7440 belongs to the T20 wedge family, a designation that refers to its physical base style. The wedge base design allows the bulb to be inserted and secured without a separate locking mechanism, relying instead on tension from the socket itself.
The Cadillac XT4 uses the 7440 for its back up light positions in both the 2021 and 2023 model years.
At 12 volts and 21 watts, the 7440 operates on the standard automotive electrical system voltage and draws a moderate wattage consistent with a single-filament reverse light application.
The single-filament construction of the 7440 distinguishes it from dual-filament variants in the T20 family, such as the 7443. The 7443 shares the same T20 wedge housing but carries a second filament and an additional contact point, making the two types physically incompatible despite their similar appearance.