Radio, Stereo, and Compact Disc: Description and Operation

System Description

Overview
The audio unit acts as the "processor" for all audio functions. Selection of the audio functions can be done from the front panel, the audio remote (on steering wheel), or by using the navigation voice control system. The audio display provides the current front and rear audio status. For vehicles with the navigation option, additional audio information is available by touching the audio button. (See the owner's manual for more details.)

Each audio component passes its audio signal to the audio unit. In addition it communicates with the audio unit via the GA-Net bus. Any open connection in this circuit will cause audio and navigation functions to appear inoperative.

The system includes an active noise control system to cancel some of the vehicle noise. It use a sine-wave shaped sound output to cancel low frequency noise. Two microphones detect the low frequency sound, and the system outputs a canceling sound through the audio speakers.

The 6CD changer output can be directed to the audio unit. The XM can be output to the audio unit.

Overview (Refer to System Diagram)
The "center module" consists of the three main sections audio, climate, and either a faceplate assembly or navigation display assembly.

Audio Unit
The audio unit acts as the "processor" for all audio inputs including muting. Selection of the audio functions can be done from the front panel, the audio remote (on the steering wheel), or by using the optional navigation voice control system. The audio display provides the current station information. For vehicles with the navigation option, additional audio information is available by touching the audio button, (see the owner's manual for more details)

GA-Net Bus
Each audio component passes its audio signal to the audio unit. This is done internally for the CD player. Each external component like XM and other audio accessories (using the audio accessory cable) communicates with the audio unit via the GA-Net Bus. Any open connection in this circuit may cause audio, and navigation functions to appear inoperative. These include no XM station information display/control or inoperative touch screen function.

Active Noise Control (ANC)
The active noise control system works in conjunction with the audio system and ECM/PCM to negate some of the vehicle noise that occurs when the PCM reduces the number of firing cylinders. In addition the ANC unit monitors two microphones and produces an "inverse" noise signal to counteract cabin background noise.

CD Changer
The 6-CD changer in the audio unit can be controlled using the audio buttons, the audio remote control switches or by voice control with navigation models. Never use CDs or CD-R with stick-on labels. The labels can peel off and jam the mechanism.

XM Radio
The XM receiver obtains XM audio from the vehicle's XM land/satellite antenna. XM signals are transmitted from geosynchronous satellites above the earth, and from land-based repeater stations. XM station information is displayed on the audio faceplate. For navigation models, audio information is displayed on the Audio-HVAC Subdisplay Unit (upper display), or alternately on the navigation display screen by touching the "Audio" button.

Security Signal
A security signal is daisy-chained between the audio, and navigation components for integration into the vehicle's alarm system.

Navigation Function (Navigation model only)
All of the navigation signal from the navigation control unit enter the center module using the 20-Pin. The optional navigation system provides voice control for AM/FM/XM, and CD player functions. Voice control commands are communicated on the GA-Net (audio bus). When the navigation unit is giving voice guidance, only the front speakers are muted, and music continues to play in the rear. When using the voice control system all speakers are muted. Muting commands are passed on the GA-Net bus. For more information, see navigation system.

Audio-HVAC Subdisplay unit (Navigation only)
This upper display shown current climate and audio status, including the clock. The clock is set by the navigation control unit, and can be adjusted in setup.