Replace the serpetine belt - 2003 Cadillac CTS

My sincere apologies for the severly delayed response.
I am personally going back to answer your unanswered questions.

I do not know if you still need this information, however I am answering it in case you still do.

Click on the following direct Link. It has A Diagram for your Belt.

Standard Rules to Removal the Serpentine Belt with a Tensioner:
1. Find the Tensioner(s). (See Diagram on Link)
2. Using a Serpentine Belt Tensioner Tool, Or Wrench OR Ratchet, Rotate/Move the Tensioner USING THE AVAILABLE NUT (on the Pulley or Arm Base) OR the OPENING (3/8ths or 1/2 inch square opening) rotating it\moving it away from contact with the belt and towards the area where the belt is not in contact with the Tensioner Pulley. The Tensioner is spring loaded, and is hard to rotate/move.
3. Remove the loosened belt off one of the other more easily accessed Pulleys.

Standard Rules for Installing the Serpentine Belt with Tensioners:
a. Pick a Pulley that is most easily accessed. This will usually be on top. This will be the last Pulley that the belt will go on.
b. Using the Diagram: Install the new Serpentine Belt on the remainder of the Pulleys....over, under, left right.
c. Using a Serpentine Belt Tensioner Tool or Wrench or Ratchet Tool: Rotate/Move the Tensioner Pulley/Arm "away" from Belt contact area on the Tensioner. This spring is pretty hard and with a new belt, it will be even harder to install. Rotate/Move this to as-close to the maximum allowed inorder to have enough slack in the belt to get it up and over the last pulley.
d. Using your other hand - Pull the Belt up and over the Last remaining Pulley.
e. Before releasing the pressure on the Tensioner, visually inspect the remainder Pulleys and the Belts' Positioning on them

Again my apologies...
Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.Com!

http://www.2carpros.com/car_repair_information/year/2003/make/cadillac/model/cts/2003_cadillac_cts_drive_belt_routing_diagram.htm