My friend pulled a KD-G729 from his mother's car,

My friend pulled a KD-G729 from his mother's car, to install in his 2004 chevy colorado. The radio worked fine before he pulled it, and once installed in his truck, the only thing that seems to work is pushing the display button and getting the time to show. With a CD in the player, it doesn't even play the CD, no radio stations come up, ect. In fact, it does nothing at all. It is getting power obviously, but won't do anything other than time display. Is there something we are missing? Thanks in advance for any help.