Principles of Operation
PRINCIPLES OF OPERATIONAudio Unit
The audio unit can be operated while the key is in RUN or ACC. The audio unit sends AC voltage audio signals to the speakers or to the amplifier, depending on vehicle configuration. The audio unit can produce its own diagnostic trouble codes (DTCs), which can be communicated to the diagnostic tool through the controller area network (CAN), or retrieved through the audio unit self-test by simultaneously pressing presets 3 and 6.
Noise Suppression Equipment
The radio frequency suppression equipment reduces interference transmitted through the speakers by the engine ignition and electrical systems. When installing any new radio suppression equipment components, make sure that a good contact is made at all connections.
Antenna
The antenna is a fixed mast antenna mounted on the exterior of the vehicle. The antenna receives both AM and FM radio waves. The audio signals are then sent to the audio unit through the antenna cables.
Subwoofer
The subwoofer speakers are powered by the subwoofer amplifier. The enable/clip detection circuit carries out 2 functions: to turn the amplifier on, and to indicate to the audio unit when the subwoofer output distortion signal reaches a damaging level. The audio unit then clips the audio output signal to prevent damage to the subwoofer.
Digital Versatile Disc (DVD) Player
The DVD player is mounted to the headliner and provides video playback on a screen when a video DVD is played. The audio signals to the rear speakers are routed from the audio unit through the DVD player. The wake-up signal for the DVD player is sent from the audio unit through the CAN.
Satellite Audio
The satellite audio system consists of a satellite radio receiver, a satellite radio antenna, and antenna cables. The satellite radio antenna receives digital audio signals and sends them to the satellite radio receiver, where the signals are converted and sent to the audio unit (or the DVD player, if equipped). The wake-up signal for the satellite audio receiver is sent from the audio unit through the CAN.
Navigation
The navigation audio unit generates a display on a video screen. When an on-screen menu key is pressed, a new screen is displayed corresponding to the key that was pressed.
Steering Wheel Controls
The steering wheel controls consist of a specific resistor value for each function creating a voltage divider. When a switch is pressed, a specific reference voltage is sent to the audio unit. The audio unit then uses this reference voltage to determine which control input function has been selected.