Information Bus: Description and Operation

The vehicle has two module communication networks. The Standard Corporate Protocol (SCP), which is an unshielded twisted pair cable (data bus plus, circuit 914 [T/O] and data bus minus, circuit 915 [PK/LB]) and the International Standards Organization (ISO) 9141 communications network which is a single wire (circuit 70 [LB/W]) network. Both networks can be connected to New Generation STAR (NGS) Tester at one connector called the Data Link Connector (DLC). This makes troubleshooting these systems easier by allowing one smart tester to be able to diagnose and control any module on the two networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The ISO 9141 communication network does not permit inter-module communication. When NGS Tester communicates to modules on the ISO 9141 communication network, NGS Tester must ask for all information; the modules cannot initiate communications.

The SCP will remain operational even with the severing of one of the bus wires. Communication will also continue if one of the bus wires is shorted to ground or battery positive voltage (B+) or a termination resistor is lost. This faulted condition is detected and reported to the host by the module's network bus interface circuits.

Unlike the SCP, the ISO 9141 communication network will not function if the wire is shorted to ground or battery voltage (B+). Also, if one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module will fail.

Anti-Lock Brake Control Module
The anti-lock brake control module is connected to the SCP communication network. The module controls the brake pressure to the four wheels to keep the vehicle under control while braking.

Driver Door Module (DDM)
The Driver Door Module (DDM) is connected to the SCP communication network. The module controls many functions including; power windows, power locks and keyless remote. The DDM also communicates with the Driver Seat Module (DSM) to control power seat and mirror memory.

Driver Seat Module (DSM)
The DSM is connected on the SCP communication network. The DSM controls the driver power seat. The module also communicates with the DDM to control the driver seat memory and both outside memory mirror functions.

Electronic Automatic Temperature Control (EATC) module
The Electronic Automatic Temperature Control (EATC) module is connected to the SCP communication network. The EATC module controls automatic climate functions that maintain the vehicle at a constant temperature setting.

Audio Control Module (ACM)
The Audio Control Module (ACM) is connected to the SCP communication network and also to the Audio Control Protocol (ACP) communication network. The ACM communicates with the compact disc and the cellular phone transceiver.

Lighting Control Module (LCM)
The Lighting Control Module (LCM) is connected on the SCP communication network. The LCM controls both interior and exterior lighting, anti-theft functions and warning chimes.

Powertrain Control Module (PCM)
The Powertrain Control Module (PCM) is connected on the SCP communication network. The PCM controls the engine performance, electronic ignition, emission controls and on board diagnostics.

Vehicle Dynamics Module (VDM)
The Vehicle Dynamics Module (VDM) is connected to the SCP communication network. The VDM controls the vehicles air ride suspension and the variable assist steering function.

Virtual Image Instrument Cluster (VIC)
The Virtual Image Instrument Cluster (VIC) is connected on the SCP communication network. The VIC displays information received on the SCP including; speedometer, odometer, message center warnings and phone displays.

Next Generation Speed Control (NGSC) Servo
The Next Generation Speed Control (NGSC) servo is connected on the SCP communication network. The module, when activated, controls and maintains vehicle speed by actuating the throttle linkage.

Electronic Crash Sensor (ECS) Module
The Electronic Crash Sensor (ECS) module is connected to the ISO 9141 communication network. The ECS module controls the deployment of the air bags based on sensor input.

Cellular Phone Transceiver (CPM)
The Cellular Phone Transceiver (CPM) is on the Audio Control Protocol (ACP) communication network and displays information through the SCP communication network.

Remote Emergency Satellite Cellular Unit (RESCU) Module
The Remote Emergency Satellite Cellular Unit (RESCU) module is connected on the ACP communication network. It provides access to a response center that can dispatch emergency and roadside assistance.