I have a problem with my audio system. I have a full navi/widescreen/TV audio system in my car from 2002, and for few days I am only hear the songs and all audio output only from both front left speakers, all others are down. Could someone help me please as I don't know what can be. In the original standard configuration is installed a separate amplifier or is everything incorporated in the radio module? What can be the reason of this malfunction?