How to Replace A Cadillac CTS Turn Signal Bulb

Having a blown turn signal bulb can be a real pain, and might even earn you a traffic ticket! However, changing a blown bulb on your own is simple, so there's no reason to be on the road without being able to indicate your turn. Here are the easy steps to replacing the turn signal bulb in your CTS.


  • 3157 bulb
  • Pocket screwdriver
  • Trim tool


  1. Determine which bulb you need to replace and turn the front wheels as far as possible in the opposite direction. 
  2. Reach up into the wheel well and find the back of the lamp assembly. 
  3. Using the screwdriver and trim tool, remove the three trim rivets that are holding the fender guard in place. You need to turn the heads as you pry upward with the trim tool. 
  4. Behind the inner fender guard you will find the turn signal socket. Use your thumb to depress the retaining clip. 
  5. Turn the socket a quarter turn counterclockwise. You can then pull the socket out of the assembly. There is not enough wire, so the socket will not come out past the inner fender guard. 
  6. You need to remove and replace the 3157 bulb while keeping the socket close to the headlight. 
  7. Put the socket back into the assembly and turn it a quarter turn clockwise. It will clip back into place. 
  8. Put the inner fender guard back and put the trim rivets back into place. Tighten them with the screwdriver.
  9. Start your Cadillac CTS and test the turn signal.

Note: Oil on your skin can create hot spots on the bulbs. It's a good idea to wear clean gloves when handling the new bulbs (or a plastic sandwich bag if clean gloves aren't handy)