Cadillac STS front and rear side marker bulbs utilize 194 and 12961 sizes respectively. The replacement chart covers 2005 through 2011 model 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.
The Cadillac STS uses two distinct bulb types across its front and rear side marker positions: the 194 and the 12961, both of which share the T10 miniature wedge form factor but differ in wattage and classification origin.
The 194 is an ANSI-standardized bulb used in the United States and Canada, operating at 12V with a rated output of 3.78W. Its standardized status means it is produced by multiple manufacturers under the same designation.
The 12961 carries a Philips part number rather than an ANSI designation, operating at 12V and 5W. It uses a W2.1x9.5d base, which is the standard wedge base specification for T10 bulbs.
Although both the 194 and 12961 are T10 wedge bulbs, their wattage ratings differ. The 12961 draws approximately 1.22W more than the 194, which is a relevant distinction when evaluating socket load compatibility.
The front side marker positions on the Cadillac STS (2005, 2010-2011) are specified for the 194 bulb, while the rear side marker positions across the same model years call for the 12961.
The front and rear side marker positions are not interchangeable by specification, as each is assigned a different bulb type despite both being T10 wedge-base units.
The W2.1x9.5d base designation on the 12961 refers to a wedge base with a 2.1mm wire width and a 9.5mm pin spacing, which is the defining physical characteristic of the standard T10 wedge base family.