Principles of Operation

PRINCIPLES OF OPERATION

Audio 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 scan tool through the medium speed controller area network (MS-CAN), or retrieved through the audio unit self-test by simultaneously pressing presets 3 and 6.

The audio unit receives the following messages through the MS-CAN:
- Reverse signal
- Received from the parking aid module and used for muting the audio unit output when a parking aid system tone is sounded.

- Vehicle speed signal (VSS)
- Received from the anti-lock brake system (ABS) control module and used for the speed-compensated volume feature.

Both of these messages are also used by the navigation system to more accurately depict the vehicle location.

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 MS-CAN.

Single-Play Mode
In single-play mode, the audio input from the DVD player is broadcast through all of the vehicle speakers. This audio input includes the DVD player and peripheral gaming devices plugged into the DVD player.

Dual-Play Mode
In dual-play mode, the audio unit continues to control the output to the front speakers, while the DVD player controls the audio to the rear speakers and headphones.

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 radio receiver is sent from the audio unit through the MS-CAN.

Navigation
The navigation module is integrated in the audio unit and controls the operation and the interface between the user, the vehicle subsystems, and the external components. The navigation module is on the MS-CAN and can be diagnosed with a scan tool. When installing a new audio unit, it is necessary to upload the module configuration information to the scan tool. Following installation of the audio unit, download the module configuration information from the scan tool into the new audio unit.

The vehicle navigation system guides the user to a pre-entered destination. A navigation map DVD stored in the navigation module sends route calculation data to the audio unit. The audio unit audibly and visually instructs the user of the maneuvers required to arrive at the destination entered.

In order to calculate the initial vehicle position, the global positioning system (GPS) antenna is used to track several available satellites simultaneously. The GPS antenna only receives data and does not communicate with the satellites. A gyroscope, integral to the navigation module, monitors the pitch and yaw of the vehicle created during cornering or turning. Vehicle speed and reverse signals received through the MS-CAN are also used to detect vehicle speed and direction changes.

Steering Wheel Controls
The steering wheel controls consist of a series of resistors. Each steering wheel control switch function corresponds with a specific resistance value within the switch. When a switch is pressed, the audio unit monitors the change in reference voltage to determine the requested function.

Audio Input Jack
The audio input jack allows for a portable MP3 player to be connected to the vehicle audio system. When a portable MP3 player is connected, audio from the MP3 player can be played through the vehicle speakers.