By the BS Auto Supplies Editorial Team | Updated October 14, 2026 | 9 min read Quick Q&A Can you replace a Cadillac XTS HID bulb without changing the headlight assembly? Yes. The bulb is a separate, serviceable part. Replace the full assembly only when the housing is cracked, water-logged, or the lens is badly damaged. How do I know the bulb has failed? Common signs include one side...