Cadillac CTS Headlight Bulb Size

Additional Notes

• The D3S bulb is used for both high beam and low beam positions in the Cadillac CTS for the 2016-2019 model years, making it a single bulb type that serves dual functions in the headlight assembly for those years.
• D3S is a high-intensity discharge bulb that operates without an external igniter, as the igniter is integrated directly into the bulb itself. This design differs from earlier HID standards and means D3S bulbs are not interchangeable with D1S bulbs, even though both are HID types.
• The D1S bulb appears across both high beam and low beam positions for the 2003-2013 model years on CTS trims equipped with HID headlamps. Like the D3S, it is a single-ended HID bulb, but it uses a separate external igniter, which is a key technical distinction between the two types.
• For the 2008-2013 model years, the CTS was offered with either HID or halogen capsule headlamp configurations, and the bulb requirements differ entirely between the two. Installing a halogen bulb into an HID housing or vice versa is not a compatible substitution.
• The H9 bulb is specified for the high beam position on halogen capsule headlamp trims from 2008-2013. H9 is a single-filament halogen bulb with a PGJ19-5 base and is rated at 65 watts, producing a relatively high light output for a halogen type.
• The H11 bulb is specified for the low beam position on halogen capsule headlamp trims from 2008-2013. H11 uses a PGJ19-2 base, which is physically different from the H9's PGJ19-5 base. Despite their similar appearance, H9 and H11 bulbs are not interchangeable due to base differences and wattage ratings.
• The 9005XS bulb is listed for the high beam position across the 2003-2007 model years. The "XS" designation indicates a short bulb variant of the standard 9005, designed to fit housings with tighter spatial constraints. The 9005XS is not a direct substitute for the full-size 9005 in all applications.
• The 9006XS bulb is listed for the low beam position on halogen capsule headlamp trims for the 2003-2007 model years. Similar to the 9005XS, the "XS" suffix denotes a physically shorter version of the standard 9006, and fitment compatibility with non-XS variants depends on the specific housing geometry.
• For the 2005-2007 model years, the low beam position shows a split between halogen capsule and HID configurations, with the 9006XS serving halogen trims and D1S serving HID trims. The high beam position for those same years lists only the 9005XS, indicating HID was applied selectively to the low beam circuit on those configurations.
• The transition from the 9005XS and 9006XS halogen types used in 2003-2007 to the D1S HID standard that became available from 2003 onward in low beams, and then to the D3S type used from 2016 onward, reflects distinct generational changes in the headlamp system across the CTS model range.