If the CD changer is OEM, then it doesn't use the AUX input.ivanhoe said:
But the FM modulator should work fine with a little bit of tweaking every now and then as you approach a station on the frequency you're using... or you might get bleedover from an adjacent channel. In those cases you might have to switch the XM and the FM to a different frequency with less interference.
If you need to share the AUX input just add a small toggle switch in the side of your left storage box to select the input you want.