Part One
Audio System Description
Overview
The audio unit acts as the processor for all audio functions. You can select the audio functions from the audio switch panel, the audio remote (on the steering wheel), or by using the navigation voice control system. The audio display provides the current front and rear audio status. For vehicles with navigation, additional audio information is available by touching the audio button (see the Owner's Manual for more details).
Vehicles with the premium audio include XM radio, '10-11 models with the premium audio and '12 model also include HandsFreeLink (HFL) and a USB adapter for playing music from USB devices.
The XM receiver, USB adapter control unit, and the audio disc changer pass their signals to the audio unit. In addition, they communicate with the audio unit via the GA-Net bus. Any open connections or short in the wiring in the GA-Net bus circuit will cause audio (including the audio accessories) and navigation functions to appear inoperative.
The audio unit has a built-in EEPROM (electrically erasable programmable read-only memory). This memory holds the audio preset data (AM/FM radio frequency, sound settings) even when the battery power is removed.
Speed-Sensitive Volume Compensation (SVC)
The audio system is equipped with speed-sensitive volume compensation (SVC). The audio unit receives the vehicle speed pulse (VSP) from the PCM. The system processes the speed input and increases the audio system volume level as the vehicle speed increases to compensate for the various interior noises that occur at higher speeds. When the vehicle slows down, the volume returns to its normal level. The SVC has four settings: SVC OFF, SVC LOW, SVC MID, and SVC HIGH that can be adjusted using the audio unit. The SVC comes from the factory with SVC MID set as the default (see the Owner's Manual for more information).
Active Noise Cancellation (ANC)/Active Sound Control System
Both the active noise cancellation (ANC) and active sound control are built into the audio unit. Both systems help eliminate unwanted sound from entering the passenger compartment. There are two microphones mounted in the headliner, one just behind the front overhead console and the other just ahead of the overhead rear light module. The microphones listen for low frequencies entering the passenger compartment and send a signal to the audio unit. The audio unit then creates a sound wave that is sent out through the speakers to eliminate the unwanted sound.
Active Noise Cancellation (ANC) System
The ANC system works to cancel engine booming sound up to about 2,000 rpm. The audio unit receives the engine speed pulse (NEP) from the PCM and outputs a sine-wave-sound through the audio speakers to cancel low-frequency noise from the engine. The ANC system also uses two microphones to detect and monitor low frequency noise in the passenger compartment. The microphones feed information back to the audio unit which adjusts the speaker output to reduce the noise. The ANC also receives input from the door open/close (INTR LT) signal from the MICU. Anytime a door is opened, the ANC system temporarily stops working.
Active Sound Control System
The active sound control is the next generation of eliminating unwanted sound in the passenger compartment. The active sound control has a much broader range than the ANC system. In addition to the microphones in the headliner, the active sound control also receives input from the engine speed pulse (NEP) to provide various levels of sound canceling depending on changes in the engine RPM.
Telematics Muting Logic
The navigation system provides voice control for the audio, the XM, and the CD player. The navigation system uses the GA-Net bus to communicate the voice control commands to the audio unit. When using the navigation TALK/BACK button, the audio is muted on all speakers and you hear navigation sound on the front channels. When using the navigation or route guidance (RG), the front speakers provides the navigation sound and the rear speakers continue to play the audio. For more information, see the navigation and HFL sections. The outline of the muting logic is shown in this table.
USB Adapter
The premium audio system can play digital music from portable audio players, a USB drive, etc. when the device is plugged into the USB adapter. The audio unit uses the GA-Net to allow you to control the device from the audio unit when searching and playing the files. Not all players and player functions work with the USB adapter. Please see the Owner's Manual for more information.
USB Function
Music files can be stored on portable USB devices (flash drives and approved iPod products) and played through the audio unit by using the USB adapter. Although a customer can create many different folder levels on their USB device, the audio unit only recognizes two levels and automatically sorts the music to meet this requirement.
To play the music files, use the dial selector to find the folder where the music file is located, then select the album or music file (see the Owner's Manual for more information about selecting and playing USB files and approved iPod products).
USB Device Requirements
- 2.0 Full speed USB capable (maximum speed is 12 Mbps).
- At least 256 MB storage capacity.
- USB formatted to be compatible with Windows-based operating systems.
- If the USB has a security feature, like write protection, it must be turned off.
There are many different USB drives, manufacturers, and configurations with new devices being released every day, which makes it impossible to test all USB devices with the audio system. Even if the USB device has all these requirements, it may not be compatible.
To check if a USB device is compatible with the vehicle, test the USB device in a known-good vehicle of the same model and year. If the USB device does not work on the known-good vehicle, assume that it is faulty or not compatible. A USB device may work on a later year of the same model vehicle because the audio unit software is constantly updated.
The audio unit displays the folder differently than what you may see on your PC because the audio unit only recognizes two folder levels. The audio unit overwrites the data for the track order when you connect the USB device. The audio unit does not modify the music files or the structure on the USB device.
Hard drives do not support overwriting the data for the track order, which is why they are not recommended.
Reconnecting the USB Device
When you disconnect a USB device, the data for the track order remains in the audio unit's memory so when you reconnect the same USB device, the audio unit continues playing from the location where it was disconnected. If a new USB device is connected, the data for the track order is rewritten and you need to select the album or music file.