Cadillac XLR Back Up Light Bulb Size

The Cadillac XLR back up light requires unique bulb sizes 3156, 2456, and 2356 depending on the specific version of the component. Data for the bulb sizes covers the range from 2004 through 2009.

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
2009	3156
2008	2456
2007	3156
2006	2456
2005	2356
2004	2456

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T25). 12V, 27W.	3156
ANSI standard (US & Canada). Festoon bulb, specialty application. 12V.	2456
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V.	2356

Other Locations

Additional Notes

The Cadillac XLR backup light specifications span the 2004-2009 model years, with three distinct bulb types used across that range: the 3156, 2456, and 2356.
The 3156 is a single-filament wedge bulb in the T25 form factor, rated at 12V and 27W, conforming to ANSI standards for the US and Canadian markets. It is fitted to the 2007 and 2009 model years.
The 2456 is a festoon-style bulb rated at 12V, also carrying ANSI certification for US and Canadian markets. It is specified for the 2004, 2006, and 2008 model years, making it the most frequently recurring bulb type across the XLR's production run.
The 2356 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and conforming to ANSI standards. It is exclusive to the 2005 Cadillac XLR within these specifications.
The BAY15d base on the 2356 positions its two filaments at different heights, a physical characteristic that prevents it from being interchanged with single-filament bulbs such as the 3156 or the festoon-style 2456.
The T25 wedge base of the 3156 and the festoon mounting style of the 2456 represent fundamentally different socket types, meaning neither is a drop-in substitute for the other despite sharing the same 12V operating voltage.
The backup light bulb specification changes across consecutive model years of the XLR, meaning the correct bulb for one year is not necessarily compatible with an adjacent model year.