I'm installing an Xtron 9953 Android unit. I have the main wire led to the back and connected. The unit turns on but I have no sound. I'm replacing the large screen factory unit, in a 2006 4.8is. It had a DVD player, a CD player and an amplifier stacked to the left in the trunk. I have removed the DVD and CD units. someone said 'connect the blue wire on the canbus harness to 12 volt" That confused me.