Don't know about your case, but I will relate what happened to me. My Son had a Kenwood 10 disc CD changer in his truck with a Kenwood radio. The radio was stolen when his truck was broken into. He decided he wanted an MP3 player so he ordered one. I don't remember the brand, but it was CD changer compatable, but it was not a Kenwood. The plug for the Kenwood changer plugged right into the back of the new radio, but when we powered everything up the CD changer went up in smoke. Seems even though the plug is standardized, the wiring is NOT amongst these radios.
I eventually opened the CD changer up to see what the damage was. Turns out it fried a PC trace on the PC board. I soldered a jumper around the burnt portion and that CD changer has been in my truck for a couple of years working fine.