How do you replace the high mount brake light on 2003 Cadillac CTS?

Answer 1

Remove trunk liner - undo nuts (about 8) -

That will make the whole license plate mount - including reverse lights - free from the care

The third brake light is attached to the mount thing by four hex screws (if still factory)

There is usually an adhesive tape holding the light on to the mount as well, so when you remove the screws it may take a little effort---

Obviously unplug the light before pulling it off-

I did this the other day, took me about 20 min, once i got the liner out, That can be a pain, if you use a flat head with a old shirt or something on it to help prevent scratching the car- Just slide it under liner behind plastic push things-

Than just put it all back together in same way - pretty easy all in all....