Audio/Video/Entertainment/Connectivity (Service Information): Operation
The Security Gateway Module (SGW) is the Controller Area Network (CAN) gateway between the Radio, Telematics module, Data Link Connector (DLC) and the other vehicle CAN modules. An SGW fault 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) commercial frequency ranges.
The audio system components operate on battery current received through a fuse in the Power Distribution Center (PDC) on a fused ignition switch output (RUN/ACC) circuit so that the system will only operate when the ignition switch is in the RUN or Accessory positions.
The optional navigation radio system receives Global Positioning System (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 Body Control Module (BCM) receives the input from the Steering Column Control Module (SCCM). The inputs are sent over the Local Interface Network (LIN) from the remote radio switches to the SCCM. The programming in the BCM allows it to process those inputs and send the proper messages to the radio receiver over the Controller Area Network - Interior High Speed (CAN-IHS) network to control the radio volume up or down, station seek up or down, preset station advance, and mode advance functions.
On vehicles equipped with an amplifier, the radio uses a different strategy for the four channel output. The left front channel is used for Voice Recognition (VR) and navigation turn-by-turn direction audio, the right front channel is used for cellphone audio. The rear channels are used for stereo, right and left channel, output to the amplifier. The signal data from the antenna, USB or AUX inputs on the rear channels is split logically so that it appears to the occupant to be surround sound. With this channel strategy, there is the possibility of additional symptoms of "no audio" from either the navigation system or the cell phone that will not set a DTC.
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 bus, 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.