Cadillac CTS Dome Light Bulb Size

Additional Notes

• The Cadillac CTS uses two distinct dome light bulb sizes across its model years: the 12961 and the PC175, both of which fall under the T10 miniature wedge bulb family.
• The 12961 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12 volts and 5 watts.
• The PC175 is an ANSI-standardized designation recognized in the United States and Canada, also a T10 miniature wedge bulb but fitted with a printed circuit board twist-lock socket, rated at 12 volts.
• Although both the 12961 and PC175 share the T10 form factor, their base types differ. The 12961 uses a standard W2.1x9.5d wedge base, while the PC175 uses a twist-lock socket designed for printed circuit board applications.
• This base difference means the two bulb types are not interchangeable, despite their shared T10 classification.
• The Cadillac CTS (2008-2019) uses the 12961 bulb for the dome light, with the exception of the 2014 and 2015 model years, which are not represented in these specifications.
• The 2003-2007 Cadillac CTS uses the PC175 bulb for the dome light, reflecting the twist-lock printed circuit board socket design associated with that generation.
• The transition from the PC175 to the 12961 coincides with the generational change between the first-generation CTS, which ended in 2007, and the second-generation CTS, which began in 2008.