Connect ipod to cd player wit built in aux input.

Question

i just bought a cable to connect my 30gb ipod video to my pioneer deh-7800mp cd player. i plugged the cable into my ipod and in the built in aux. in the back of my cd player and when i turn my ipod on and attempt to play music nothing comes out. what do i need to do to solve this? is there a place where i gotta sync the two devices together?