Park the vehicle on a flat surface and turn off the engine.
Locate the license plate light assembly. It is situated on the underside of the trunk lid, near the license plate.
Use a flat-head screwdriver or pry tool to gently pry open the plastic cover of the light assembly.
Once the cover is removed, you will see the light bulb socket.
Twist the light bulb counterclockwise to remove it from the socket.
Insert the new light bulb into the socket and turn it clockwise until it is secure.
Replace the plastic cover of the light assembly and press it firmly until it snaps into place.
That's it; you have now successfully replaced the license plate light bulb in your 2005 CLK 320.
