Do you have the invision headset system? If so, use the remote control to set the FM modulation on and off to see if that does something. It's only on the remote. When set in this mode, do you actually hear something through the radio tuned to the frequency?
I believe the rear zone on/off only has to do with the ability of people in the back to use the center console audio controls.
I believe the rear zone on/off only has to do with the ability of people in the back to use the center console audio controls.