Principles of Operation

PRINCIPLES OF OPERATION

Audio Unit
The audio unit can be operated while the key is in RUN or ACC. The accessory delay feature allows the audio unit 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 audio unit sends AC voltage audio signals to the speakers or to the amplifier, depending on vehicle configuration. The audio unit 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 audio unit self-test by simultaneously pressing preset buttons 3 and 6. The audio unit communicates via the MS-CAN.

Front Display Interface Module (FDIM)
The FDIM displays information from multiple inputs, including the audio unit, climate control, and instrument cluster, depending on configuration. Data from these modules is transmitted via the MS-CAN.

Front Control Interface Module (FCIM)
The FCIM is the customer interface to the audio unit. It is separate from the audio unit, and utilizes the MS-CAN to send button press information to the audio unit.

Satellite Audio
The satellite audio system consists of a satellite radio receiver, a satellite radio antenna, and an antenna cable. The satellite radio antenna receives digital audio signals and sends them to the satellite radio receiver, where the signals are converted and sent to the audio unit. The satellite radio receiver communicates via the MS-CAN.

Antenna - AM/FM
The fixed-mast antenna receives AM/FM radio waves and sends them to the audio unit via the antenna co-axial cable.

Subwoofer
The Audiophile subwoofer and amplifier are integral. The enable/clip detection circuit carries out 2 functions: to turn the amplifier on, and to indicate to the audio unit when the subwoofer output distortion signal reaches a damaging level. The audio unit then clips the audio output signal to prevent damage to the subwoofer.

Navigation
The navigation audio unit generates a display on a video screen. When an on-screen menu key is pressed, a new screen is displayed corresponding to the key that was pressed. For Hybrid vehicles, the navigation audio unit also displays an energy flow graphic. The navigation audio unit receives this information via the MS-CAN.

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 audio unit 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 unit
- Navigation audio unit
- Satellite radio receiver
- FDIM
- FCIM

The following messages are utilized by the audio system:







IDS Scan Tool Acronyms
The IDS scan tool uses the following acronyms for modules addressed: