Cadillac XTS high beam and low beam headlight bulbs both use D3S size bulbs for optimal illumination. The replacement chart covers 2013 to 2018 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.
ECE standard (Europe & worldwide). Mercury-free HID (xenon) discharge bulb with PK32d-5 base and integral ignitor, for projector-type housings. 42V, 35W.
The D3S is the sole bulb type specified for the Cadillac XTS across both high beam and low beam headlight positions for the 2013-2018 model years.
The D3S is a high-intensity discharge (HID) bulb, which operates by passing an electrical arc between two tungsten electrodes within a quartz envelope filled with xenon gas and metal halide salts.
The "D" prefix in the D3S designation indicates the bulb belongs to the automotive HID discharge family, while the "S" suffix denotes a single shroud surrounding the arc tube, which controls light distribution and reduces glare.
D3S bulbs operate without a separate igniter, as the ignition circuitry is integrated into the ballast unit, distinguishing them from D1S bulbs, which require an external igniter module.
The D3S standard is mercury-free, a characteristic that differentiates it from the D2S and D4S types, which differ in operating voltage and chemical composition of the arc fill.
Because the Cadillac XTS uses the same D3S bulb for both high and low beam functions, the headlight system relies on a projector or bi-xenon mechanism to switch between beam patterns rather than separate bulb units.
D3S bulbs are not interchangeable with D1S or D2S bulbs despite sharing a similar physical form, as differences in base configuration and electrical requirements prevent cross-fitment without modification.
The consistent D3S specification across all six model years indicates no bulb type change occurred within the XTS headlight system during the 2013-2018 production span.