Principles of Operation

PRINCIPLES OF OPERATION

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

Audio 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 amplifiers, 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.

Satellite Audio
The satellite audio system consists of a satellite digital audio receiver system (SDARS) module, a satellite radio antenna, and a satellite radio 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 ACM. The SDARS module communicates via the MS-CAN.

Antenna - Fusion, Milan
The antenna receives AM/FM radio waves, and satellite audio signals (if equipped with satellite audio). The AM/FM antenna sends audio signals to the ACM. The satellite radio antenna receives digital audio signals and sends them to the SDARS module.

Antenna - MKZ
The antenna receives both AM and FM radio waves. The antenna is built into the rear window glass and has a module to interpret the audio signals. The audio signals are then sent to the ACM through the antenna cable. If equipped with satellite audio, the satellite radio antenna is mounted to the roof. It receives digital audio signals and sends them to the SDARS module.

Subwoofer
The subwoofer speakers are powered by the subwoofer amplifier (Audiophile) or by the audio digital signal processing (DSP) module (THX(R) only). 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 Digital Signal Processing (DSP) Module
The DSP module 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, 1 rear/center speaker, and 2 subwoofer speakers.

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 ACM communicates with other vehicle systems via the medium speed controller area network (MS-CAN) and can be diagnosed with a scan tool.

The vehicle navigation system guides the user to a pre-entered destination. A navigation map DVD stored in the navigation module sends route calculation data to the ACM. The ACM audibly and visually instructs the user of the maneuvers required to arrive at the destination entered.

In order to calculate initial vehicle position, the global positioning system (GPS) antenna is used to track several available satellites simultaneously. Vehicle speed and transmission gear selected signals received through the MS-CAN are also used to detect vehicle speed and direction changes.

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 ACM.

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:
- ACM
- Navigation ACM
- SDARS module
- DSP module

The following messages are utilized by the audio system:

Audio System (Part 1):

Audio System (Part 2):