Communications Network
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 the scan tool at one connector called the data link connector (DLC). This makes testing and diagnosing these systems easier by allowing one smart tester 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 the scan tool communicates to modules on the ISO 9141 communication network, the scan tool must ask for all information; the modules cannot initiate communication.
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.
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. For additional information, refer to ANTI-LOCK CONTROL - TRACTION CONTROL .
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. For additional information, refer to KEYLESS ENTRY/COMPUTER OPERATED LOCKS .
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. For additional information, refer to SEATING .
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. For additional information, refer to AUTOMATIC A/C-HEATER SYSTEMS .
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. For additional information on the cellular phone, refer to TELEMATICS .
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.
For interior lighting, refer to INTERIOR LIGHTING . For exterior lighting, refer to EXTERIOR LIGHTING .
For active anti-theft, refer to ANTI-THEFT - PERIMETER . For passive anti-theft, refer to ANTI-THEFT - PATS . For warning chimes, refer to WARNING DEVICES .
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. For additional information, refer to SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV .
The vehicle dynamics module (VDM) is connected to the SCP communication network. The VDM controls the vehicle's air ride suspension and the variable assist steering function. For additional information; refer to VEHICLE DYNAMIC SUSPENSION .
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. For additional information, refer to INSTRUMENT CLUSTER & PANEL ILLUMINATION .
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. Refer to VEHICLE SPEED CONTROL .
The restraint control module (RCM) is connected to the ISO 9141 communication network. The RCM controls the deployment of the air bags based on sensor input. For additional information, refer to AIR BAG RESTRAINT SYSTEMS .
The cellular phone transceiver (CPM) is on the audio control protocol (ACP) communication network and displays information through the SCP communication network. For additional information, refer to TELEMATICS .
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. For additional information, refer to TELEMATICS .