Audio/Video/Entertainment/Connectivity (Service Information): Operation
The Security Gateway Module (SGW) is the Controller Area Network (CAN) gateway between the radio, telematics modules, Data Link Connector (DLC) and the other vehicle CAN modules. An SGW failure could prevent the radio from powering up, telematics module from communicating or a scan tool from communicating with the vehicle. For additional information on the SGW. Refer to MODULE, SECURITY GATEWAY (SGW), DESCRIPTION .
Use of the MIT019 Multi-Media Tester may cause the radio screen to go blank.
The audio system components are designed to provide audio entertainment and information through the reception, tuning and amplification of locally broadcast or satellite, (if equipped) radio signals in both the Amplitude Modulating (AM) and Frequency Modulating (FM) and Satellite Digital Audio Radio Service (SDARS), if equipped, commercial frequency ranges.
The SGW is in the audio and telematics systems to provide security against certain types of attacks and threats from the scan tool, telematics and entertainment buses, which can put the rest of the vehicle's buses at risk of intrusion. The SGW lies electrically between the vehicle on one side, and the Data Link Connector (DLC), telematics and entertainment systems on the other side. The main function is to gate messages from one bus to another. The SGW monitors the B(+) Feed, switched ignition feed, CAN circuits, software and hardware for any concerns.
The audio system operates on a non-switched fused B(+) battery current source and is turned ON or OFF by electronic messages received over the Controller Area Network (CAN) data bus so that the system will only operate when the status of the ignition switch is RUN or Accessory.
The optional navigation radio system receives GPS signals from up to eight satellites to display the position and direction of the vehicle. An electronic gyro-sensor and the vehicle's speed sensor enable the system to display the present vehicle position even in locations where GPS signals may be blocked.
When a destination is selected, the navigation system uses information from the map to quickly calculate a route. As the vehicle is driven along the chosen route, the operator is guided with pictorial displays and voice prompts.
On vehicles that are equipped with the optional remote radio switches, the remote radio switches send their multiplex signal input directly via hardwired connection to the Electronic Vehicle Information Center (EVIC) switch. The EVIC sends the remote radio switch signals to the Steering Column Control Module (SCCM) over the Local Interface Network (LIN) data bus. The SCCM then broadcasts the LIN bus message to the SGW on the CAN data bus where it is checked for being an allowed message, then sent to the radio on the CAN data bus to control the radio volume up or down, station seek up or down, preset station advance, and mode advance functions.