Audio System
AM/ FM Radio
The audio unit antenna receives AM/ FM radio waves containing data. The data is sent through the audio unit antenna cable to the ACM. The radio waves are converted into fluctuating AC voltage and sent as analog audio signals to the speakers.
To prevent voltage spikes from producing popping noises through the speakers when the ignition is in the START mode, the ACM receives a voltage signal from the PCM-controlled starting circuit. When the ACM detects the voltage signal from the starting circuit, the audio signal output mutes.
Satellite Radio (if equipped)
The satellite antenna sends data through the satellite radio cable to a splitter (integrated into the cable). The satellite radio data is separated from the GPS data and sent to the satellite radio receiver within the ACM. The metadata is displays on the touchscreen display and the audio data is converted and sent to the speakers in the same manner as the AM/ FM radio.
Accessory Delay Feature
The accessory delay feature is a BCM-controlled function that allows the audio system to be operated for a preset period of time after the ignition is turned off and a front door has not been opened.
Battery Load Shed Feature
The BCM uses the battery current sensor to monitor the battery state of charge. When conditions exist to cause the battery load shed feature to activate, the BCM deactivates the battery saver relay (internal to the BCM) and a message is sent over the CAN to turn off selected systems. This turns the audio system off to save the remaining battery charge. To activate the battery saver relay, start the vehicle.
Chimes
Various vehicle systems send chime requests over the CAN to the IPC. The following are determined as the IPC processes these requests:
- Chime characteristics such as tone, tone length, number of repetitions, and time between tones
- Chime output volume
- Priority of the chime request
- Specific speakers (front, rear or all) to sound chime
The IPC sends the processed requests over the CAN to the ACM. The ACM outputs the left and right analog chime tones to the appropriate audio system speakers as fluctuating AC voltage.
For specific chime information, Refer to: Warning Chimes - System Operation and Component Description .
Speed Compensated Volume Feature
The ACM compensates for wind and road noise by adjusting the audio system volume based on the vehicle speed provided by the PCM over the CAN and the speed compensated volume setting.
ESE (vehicles equipped with 3.5L GTDI)
The ESE is an audio system feature that enhances certain engine tones typically induced under wide open throttle or heavy part-throttle conditions.
The ESE system uses a DACMC (integrated into the ACM) and the audio system speakers.
The DACMC determines the engine tone to enhance based upon engine rotation speed data, engine torque data, and accelerator pedal position data from the PCM. The data from the PCM is processed and converted to an audio signal, transmitted to the DACMC internal tone generator, and output by the ACM to the front door speakers as fluctuating AC voltage.
Steering Wheel Audio Controls
The audio/SYNC steering wheel switch contains a series of resistors. Each steering wheel switch function corresponds with a specific resistance value within the switch.
The SCCM sends 5 volt reference voltages to the audio/SYNC steering wheel switch. When a switch is pressed, the voltage is routed through the corresponding resistor to the return circuit through the clockspring to the SCCM. The SCCM monitors the resultant voltage drop to determine the button pressed on the switch.
The audio/SYNC steering wheel switch inputs are sent as network messages from the SCCM to the ACM to control audio functions.