Blinker out on '05 CTS

Turn off your Cadillac CTS and look below the front grille for the bottom pins that hold it in place. Push these pins inward to disengage them.

2 Open the hood. Look for the pins that hold the grille in place on the engine compartment side. Push in these pins. Pull the grille off the front of the Cadillac CTS.

3 Remove the side pins from the CTS fender on the side that has the headlight you wish to replace. Pull the side fender away from the vehicle to prepare for removing the headlight.

4 Remove the three bolts on the top and rear of the headlight.

5 Disconnect the wiring harness from the back of the headlight.

6 Push or pull the headlight through the front of the Cadillac CTS and set it aside. This part may require a lot of force if the headlight is stuck.

7 Insert the new headlight along the runners upon which the previous headlight sat, and attach the wiring harness. Reinstall the three bolts you removed earlier, as well as the side finder and the grille.

I replaced the front turn signal bulb on my 2004 CTS. I removed about 4? screws holding the inner fender to the outer fender, just forward of the tire. Then you reach your hand in and find the socket. Twist the socket about a quarter turn to unscrew it and remove the socket. As I recall the bulb is pulled straight out of the socket.

Sorry to reply so late.
It's got to be the same as my 2004 CTS...
Remove 3 or 4 of the plastic pins holding the inner fender. They are located around the lip of the fender opening. The pins are removed by pulling the center cap of the pin straight out about an 1/8" and then wiggle and pull the whole pin out.
Pull the inner fender down and back.
Reach your arm in and grab the socket and squeeze the locking tab.
Rotate the socket counter-clockwise less than a quarter turn, and pull straight back.
Reach your other hand in and remove the bulb by pulling it straight out of the socket. It takes a 3157 bulb

The fender liner needs to be removed. It takes the removal of up to 20 plastic pins. Once it is out of the way the bulb sockets become available. twist the bulb socket counterclockwise and the bulb can be pulled out. Reverse order for reinstallation

Remove 3 or 4 of the plastic pins holding the inner fender. They are located around the lip of the fender opening. The pins are removed by pulling the center cap of the pin straight out about an 1/8" and then wiggle and pull the whole pin out.
Pull the inner fender down and back.
Reach your arm in and grab the socket and squeeze the locking tab.
Rotate the socket counter-clockwise less than a quarter turn, and pull straight back.
Reach your other hand in and remove the bulb by pulling it straight out of the socket. It takes a 3157 bulb

no more like a 3157 check old bulb should have # on it

Remove the upper air intake splash shield.
Remove the headlight retainer nuts (2)
Remove the headlight/blinker assembly
Carefull the blinker has a retainer post with a rubber retainer on the fender
Remove bulb

It is fairly simple to replace the turn signals on the CTS. You do not have to remove the whole bumper, just enough to let you inside behind the lights. Turn the steering wheels one way and remove the 4 clips around the bumper with a flathead screw driver. Then do it again to the other side. You can remove the top clips to give you more wiggle room. Look under the car and remove enough of the clips to loosen the sides. At this point you can stick in your hand from the wheel well and replace the lights. Just turn and pull and re-install the new lights. Simple.

changing the blinker on a CTS

To replace the headlight bulb on your cts, it is kinda a pain. You pretty much have to take the whole front bumper off. First remove all of the push pins that hold the air deflector on the bottom. Next remove the pushpins that hold the grille to the tie bar. Now remove the front fascia extension. Remove the bolts that hold the bumper to the fender. Once all the bolts are out that hold the bumper on, you gently pull out on the bumper, but be careful not to crack it. If the windshield washer hoses are connected to it then you need to disconnect them, but you may want to plug the line so you don't loose all the washer fluid. Next there are two bolts and a nut that you remove to take the headlight out, and remove the connectors that go to it.