Principles of Operation
Information and Entertainment System
Principles of Operation
NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
Audio Control Module (ACM)
The audio system can be powered up when the ignition is in the ON or ACC position. When on, the Audio Control Module (ACM) directs audio signals to the speakers through separate positive and negative circuits for each of the audio channels. The ACM provides internal circuit protection for shorts to ground, shorts to voltage, or shorts between any output circuits.
Noise Suppression Equipment
The radio interference suppression equipment reduces interference transmitted through the speakers by the engine ignition and electrical systems.
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 ACM through the antenna cables.
Subwoofers
The subwoofer speakers on the 500-watt system are located in the front doors and are powered by individual amplifiers located on each speaker. In addition to these subwoofer speakers, the 1000-watt system includes an enclosure with 2 subwoofer speakers powered by 2 amplifiers, each. 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 ACM clips the audio output signal to the subwoofer amplifier (heard as distortion).
Satellite Audio
The satellite audio system consists of the Satellite Digital Audio Receiver System (SDARS) module, a satellite radio antenna, and antenna cable (part of the decklid harness). The satellite radio antenna receives digital audio signals and sends them to the SDARS module, where the signals are converted to analog and sent to the ACM. The wake-up signal for the SDARS module is sent from the ACM through the Medium Speed Controller Area Network (MS-CAN).
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.
Navigation
The navigation module is integrated in the ACM and controls the operation and the interface between the user, the vehicle subsystems, and the external components. The navigation module communicates with other vehicle systems via 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 ACM. The ACM 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.
Network Communication
The following audio system components communicate via the MS-CAN:
- ACM
- Navigation ACM
- SDARS module
The following messages are utilized by the audio system:
