Cadillac CTS Drivers Side Signal Light
 

Actually, the method of gaining access to the sidemarker light is by removing the front facia, including the grille and front bumper cover. Prepare for that if you ever need to work on the headlights, too. Before you pull all that stuff off, I would remove the plastic "air deflector" from underneath the front of the car. You have to do this anyway to remove the facia. See if you can reach up to the side marker from there. The light assembly is only held in with a clip, press the tab and push the top of the cornering lamp outward. Lift up on the cornering lamp in order to remove it from the facia. This info came from my 05 CTS service manual. I think it should be pretty much the same for an 04. Good luck and let us know how it works out.

Thanks so much!
Is it rather, hard ... to take off the whole front facia?

I have not tried it yet myself, but it's only a matter of time until some light or other burns out. It just seems like alot of work to change a bulb or lens. Now that I look at the directions a little more closely, (and the accompanying drawings which suck) it says to remove the "front fascia extension", not the whole front fascia. And if I'm looking at this correctly, the "extensions" are the plastic pieces inside the wheel well towards the front of the car. They appear to be held in with plastic push pins which you just pull the center out to release them. THAT makes a whole lot more sense. It looks like a splash shield, behind the headlight assembly and in front of the tire. If you take that one piece out you should be able to get to the side marker light.

Okay Thank You, that seems to make a tad more sense then having to take off the whole .. front .. end !
Thanks so much, you seem to be a lot of help with other CTS owners. Do you have anymore pictures of your CTS up ?

Yes, there are 3 on page 8 (at the moment) of the photo gallery. The title is "05 CTS" and it lists the owner as Venomous Duck, which was another screen name I used for a while. I splurged and bought the service manual shortly after I bought my car. It has a lot of good info in it but it is a fairly expensive set of books. So, if I can help, I try to. Keep us all posted on how it works out for you and if you learn any thing along the way, by all means, share. Mike.

did yours not come with the manual ?

I'm not talking about the owners manual, that little book that fits in the glove box. I'm talking about the "Service Manual". It's a 3 volume set of books that are each about 2 1/2 inches thick and weighing in at 17.4 pounds. It's the printed version of what the mechanics use to troubleshoot and repair the cars. It has drawings and descriptions of how to remove and replace just about everything on the car. Troubleshooting is a little difficult because it assumes you have access to Computer Diagnostic Tools. (which I don't) But it's been pretty helpful in figuring out how to access those pesky side marker lights!

Thanks a bunch!
I do know what you're talking about... those big, beastly books. You can find them at big libraries.