Well I have a CD player like that too, It is the original GeneralMotors player.
Standard PC 5 1/4 inch with some mounting rail attached to it, the CD player is
controlled by the original GM head unit. (Which I've ripped out.)
I did some probing with my scope, enough to realize that the traffic on the GM
bus was 2 ways. -> gave up on it. (I was hoping that I could just power the CD drive up, put a CD in it, and it would play, but no. It needs the GM headunit.)

TommyE