Principles of Operation
PRINCIPLES OF OPERATIONAudio Control Module (ACM)
The ACM can be operated while the key is in RUN or ACC. The accessory delay feature allows the ACM to be operated for a preset period of time after the key is moved to OFF and a front door has not been opened. The ACM sends AC voltage audio signals to the speakers or to the amplifier, depending on vehicle configuration. The ACM can produce its own DTCs, which can be communicated to the scan tool through the medium speed controller area network (MS-CAN), or can be retrieved through the ACM self-test by simultaneously pressing presets 3 and 6. The ACM communicates via the MS-CAN.
Satellite Audio
The satellite audio system consists of a satellite digital audio receiver system (SDARS) module, a satellite radio antenna, and an antenna cable. The satellite radio antenna receives digital audio signals and sends them to the SDARS module, where the signals are converted and sent to the audio rear control unit (RCU) (or the rear seat entertainment module [RETM], if equipped). The SDARS module communicates via the MS-CAN.
Antenna - AM/FM
The combination AM/FM antenna is located on the right rear quarter-glass. An antenna amplifier is used to amplify the signals to the ACM. The AM/FM antenna cannot be replaced separately from the quarter glass.
Subwoofer
The Audiophile subwoofer and amplifier are integral. The subwoofer in the THX(R) audio system is powered by the audio digital signal processing (DSP) module. The enable/clip detection circuit carries out 2 functions: to turn the amplifier on, and to indicate to the ACM when the subwoofer output distortion signal reaches a damaging level. The ACM then clips the audio output signal to prevent damage to the subwoofer.
Audio Rear Control Unit (RCU)
The RCU allows rear-seat users to select audio functions. It allows for single/dual-play mode. The RCU communicates via the MS-CAN.
DVD Entertainment System
When a video disc is inserted and the PLAY button is pressed, an image is displayed on the screen and a stereo signal is transmitted to the ACM. The DVD entertainment system allows for single/dual-play mode. The rear seat entertainment module (RETM) communicates via the MS-CAN.
Single-Play Mode
In single-play mode, any audio input routed through the RCU (or RETM) is broadcast through all of the vehicle speakers. These audio inputs include the DVD audio and peripheral gaming devices plugged into the RCU (or RETM).
Dual-Play Mode (All Audio Systems Except THX(R))
In dual-play mode, the ACM continues to control the output to the front speakers, while the RCU (or RETM) controls the audio to the rear speakers and headphones.
Dual-Play Mode (THX(R))
In dual-play mode, the ACM continues to control all of the vehicle speakers. The RCU (or RETM) controls the audio output to the headphones only.
THX(R) Audio System
The THX(R) audio system provides theatre quality sound in the vehicle. Audio signals are sent to the DSP module, which processes the audio signals and sends them to the 12 speakers: 4 door speakers, 2 tweeter speakers, 3 front/center speakers, 2 D-pillar tweeters, and a subwoofer. The DSP module communicates via the MS-CAN.
Navigation System
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 ACM 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 map DVD stored in the navigation ACM is used for calculating the vehicle course. The ACM audibly and visually instructs the user of the maneuvers required to arrive at the destination entered.
A voice recognition system allows the user to interface with the system without using the touch screen. A microphone located in the rear view mirror provides a direct input to the navigation module.
In order to calculate initial vehicle position, the global positioning system (GPS) antenna is used to track several available satellites simultaneously.
The vehicle speed signal (VSS) and transmission gear selected signal are received by the navigation ACM through the MS-CAN. These signals are used to increase the accuracy of the displayed course.
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 ACM 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.
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.
Network Communication
The following audio system components communicate via the MS-CAN:
- Audio control module (ACM)
- Navigation ACM
- Satellite digital audio receiver system (SDARS) module
- Audio rear control unit (RCU)
- Rear seat entertainment module (RETM)
- Audio digital signal processing (DSP) module
The following messages are utilized by the audio system:
Audio Signal Flow
The following illustrations depict the audio signal flow.
Without THX(R) Sound:
With THX(R) Sound:
