Although some 2003 Cadillac DeVille models may be equipped with non-serviceable LED (Light Emitting Diode) taillights, the headlights on all models are standard halogen bulbs. These are simple to replace, even on a high-tech car such as the DeVille. Use only the GM-recommended replacement bulbs for your Cadillac; installing other bulbs, if they fit at all, could cause problems.
Turn the engine off. Open the hood to access the headlight casing.
Remove the push pins that attach the protective panel (along the front of the engine bay, over the headlights). Use a screwdriver to depress the center of the push pins, and then pull them out. Pull the panel away when all of the push pins are removed.
Remove the three bolts from the top part of the headlight casing. Push the backside of the casing forward, toward the grille.
Grasp the edge of the headlight casing exposed above the bumper. Pull the headlight casing out carefully.
Pry off the bulb dust cover from the rear of the casing (with the screwdriver). Rotate the bulb socket counterclockwise to release it from the casing.
Pull the bulb straight away from the socket. Attach the replacement bulb. Do not touch the glass; instead, hold the bulb by its plastic connection module.
Reinsert the bulb into the rear of the casing. Rotate it clockwise to secure it, and then push the casing back into the mount. Tighten the three bolts, with the socket wrench.
Set the plastic panel back in place. Align the holes in the panel with the push pin mounting holes in the engine bay. Replace the push pins; push down on the outside rim of the pins to secure them.
