Headlamp Bulb not working on 2003 Cadillac Deville

That is a three element lamp bulb. Brakes, turn, and tail lights are all in the same bulb. Replace the bulb and all should be OK.

To get at it, you will need to pull the license plate bezel by removing the retaining nuts inside the trunk.

Check the socket for corrosion. If there is some clean it up and see if the light works. If there is no corrosion or if the light still doesn't work after cleaning the socket then test the low beam circuit for power. If there is no power consult an auto electric shop or the dealer.

On this website you find fuse box diagram and description for Cadillac DeVille (2003 - 2004)


https://www.carknowledge.info/cadillac-deville-2003-2004-fuse-box-diagram

To remove first you want to remove the headlight door mounting screws and remove the headlight door. Then you want to remove the 4 retainer ring screws and remove the retainer ring from the headlight. Then you want to pull the headlight bulb forward and detach the wiring connector.

To install you first want to attach the wiring connector to the headlight bulb and place the bulb in position, locating the bulb glass tabs in the positioning slots. Then you will attach the bulb retainer ring to the assembly with the retainer ring screws. Then you will install the headlight door and secure with the screws. Then you will check the headlight bulb aim and adjust as necessary

Let me know if this helps you.

Hello Did you check both front and rear? Did you compare the working side (right) to the left side? Some applications have more than one bulb. Hope this helps

Generally the low beams or high beams for that matter are a bulb that connects to a socket that is held in place by a ring or collar that is rotated to release from behind the glass and plastic headlamp assembly. Open the hood to access it, generally.
May have to remove a shroud or plastic paneling to get to it.

If you get your bulbs from the parts store, looking at the base can give you a clue as to how to replace it on the car. Make sure the O-ring seats properly and do not handle the bulb without gloves or shortly after turning off the lights (removing old bulb).

Take it to someone else would be the easiest. On that engine you have to pull the intake. The starter is just under the intake. Not a hard job. I wouldn't call it a job for a beginner.

1.Change the bulb
2.Fuses

check the socket the bulb goes into