How to change driver side headlight bulb for my 2013 Cadillac XTS

remove the washer bottle filler neck. In order to remove it you'll need to give it a good pull straight up. There are no bolts holding it. Once removed, you can access the cover for the headlamp bulb. It is round with a raised section down the middle. twist it counter clockwise to remove. After removal, you will see a small metal box with an electrical wire bundle plugged in. Remove plug and turn counter clockwise. That's it, the bulb is now in your hand.

It is a tight space, but once the windshield washer filler is removed, there is enough room to remove the ballast and bulb. Remember never to touch the bulb of the HID portion. Oily fingerprints can cause the bulb to fail if it is the HID type.