Cadillac CTS Stepwell Bulb Size

The Cadillac CTS stepwell uses 12961 and 906 bulb sizes for the interior lighting components located near the floor. Available data for the specified vehicle covers the range from 2005 through 2019.

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
2016-2019	12961
2008-2013	12961
2005-2007	906

Bulb Specifications

Description	Bulb Size
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 8W.	906

Other Locations

Additional Notes

The Cadillac CTS stepwell uses two distinct bulb sizes across its model years, the 12961 and the 906, both of which share the T10 miniature wedge form factor.
The 12961 is a Philips part number designation for a T10 miniature wedge bulb rated at 12V and 5W, fitted with a W2.1x9.5d base.
The 906 is an ANSI standard designation recognized in the US and Canada, also a T10 miniature wedge bulb, but rated at a higher wattage of 12V and 8W.
Although both bulbs share the T10 wedge form factor, the 906 draws 8W compared to the 12961 at 5W, meaning the two are not electrically equivalent and are not interchangeable without consideration of that difference.
The W2.1x9.5d base specification of the 12961 describes a wedge-type base with a 2.1mm wire width and a 9.5mm insertion depth, which defines its physical fitment into the socket.
The Cadillac CTS (2008-2013) and (2016-2019) model years specify the 12961 bulb for the stepwell position.
The 2005-2007 model years specify the 906 bulb for the stepwell position.
The shift from the 906 to the 12961 between the 2007 and 2008 model years represents a change in both the wattage rating and the part number standard used, moving from an ANSI designation to a Philips manufacturer designation.