Principles of Operation

PRINCIPLES OF OPERATION

Audio System

NOTE: The audio unit is also referred to as the audio control module.

The audio unit can be powered up when the ignition is in the ON or ACC position.

When on, the audio unit directs audio signals to the speakers through separate positive and negative circuits for each of the 4 audio channels: LH front, RH front, LH rear, and RH rear. The audio unit provides internal circuit protection for shorts to ground, shorts to voltage, or shorts between any output circuits.

The subwoofer speaker is powered from a separate subwoofer amplifier. The enable/clip circuit carries out 2 functions: to turn on the subwoofer amplifier, and to monitor an overload condition to the subwoofer amplifier. In the event of an overload, the audio unit clips the audio output signal to the subwoofer amplifier (heard as distortion).

The digital versatile disc (DVD) player receives a wake up signal from the audio unit through the medium speed controller area network (MS-CAN). When a video disc is inserted into the DVD player and the PLAY button is pressed, an image is displayed on the screen and a stereo signal is transmitted to the audio unit.

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. The wake-up signal for the satellite radio receiver is sent from the audio unit through the CAN.

The radio suppression equipment reduces interference transmitted through the speakers by the engine ignition and electrical systems.

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.

Navigation System
The navigation module is integrated into 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.

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 CAN are also used to detect vehicle speed and direction changes.