Fog lights are the smaller lamps mounted in the bumper of the X300. They aren't as bright as headlights, but they are ideal for driving in fog. Fog reflects the strong illumination from the headlights back into the eyes of the driver. Fog lights are halogen bulbs and rarely burn out. If you need to replace yours, you can do it yourself by removing the fog light assembly, then replacing the bulb inside. You can buy replacement bulbs from your Jaguar dealer or from auto parts stores.
Remove the undertray from the front of the car. It is held in by clips held in place by screws. Unscrew the screws, then depress the clips to remove it. Set the tray and screws aside.
Turn the wheels in the opposite direction of the lamp you want to work on. This gives you more room behind the wheel well. Jack up the front of the car on the side of the fog light you wish to remove.
Reach under the bumper and unplug the wire going into the back of the fog light. Press the button on the top of the connector plug while pulling the plug straight backward.
Depress the clips on either side of the fog light assembly using a flat-tip screwdriver. Press both at the same time. They are very stiff; you may need someone to help.
Push on the back of the fog light assembly while holding down the clips. It will pop out of the bracket.
Open the fog light assembly by removing the black plastic frame and disk on the back. They are held in by simple clips. Pry up the clips and they will pop out.
Unplug the fog light from the connector and squeeze the metal clips on either side of the base. The bulb will come right out.
Insert a new bulb by pressing it into the socket. You will hear a click when it seats. Plug the wire into the back of the bulb, then replace the plastic frame and disk.
Insert the fog light assembly back into the socket in the bumper. Make sure you're putting it in right-side up. It will click into place.
Plug the power connector from the car into the back of the fog lamp. Turn the car on and test the lights before you replace the undertray.
Clip the undertray back into place, then screw in the screws.