Cadillac CTS First Generation Forum - 2003 - 2007 Discussion, Radio not working in Cadillac CTS Coupe, Sport Sedan and Sport Wagon Forums; I did not dissconnect the battery when i did the swap. I am not 100 percent sure the a.m. worked ...
part numbers often change/supercede so the exact number might not match but you will need the same radio
i can check part numbers to see if the replacement matches your part number if it's not an exact match
a dealer will need to program the radio to your car and will need some extra info to ensure that the radio isn't stolen (usually a proof of purchase or something like that... they will let you know what their policy is)
I'm dealing with the same issue with my CTS. I ended up taking it to the dealer after I replaced the antenna module and checked all of the fuses, connections etc. The dealer had it for a few days and the only thing they could come up with was a bad radio. My remotes did not work after I replaced the antenna module and from what I have read it does need to be programmed to vehicle.