Scheme 1
Principles of Operation
The vehicle has three module communication networks. Only two of these networks are connected to the diagnostic connector. The standard corporate protocol (SCP), which is an unshielded twisted pair cable: data bus plus and data bus minus and the International Standard Organization (ISO) 9141 communication network, which is a single wire network. The audio control protocol (ACP), which is an unshielded twisted pair cable this networks can only be accessed through the SCP network. Both SCP and ISO networks can be connected to the PDU tester by one connector called the diagnostic connector. 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 diagnostic connector is located under the instrument cluster panel, between the steering column and the audio unit.
The ISO 9141 communications network does not permit inter-module communications. When the PDU tester communicates to modules on the ISO 9141 communication network , the PDU must ask for all information; the modules initiate communications.
The SCP communication network will remain operational even with severing of one of the bus wires. Communications will also continue if one of the bus wires is shorted to ground or battery positive voltage (B+), or if some, but not all, termination resistors are lost.
Unlike the SCP communication network, the ISO 9141 communication network will not function if the wire is shorted to ground or battery positive voltage (B+). Also, if one of the modules on the ISO 9141 network loses power or shorts internally, communication to that module will fail.
The anti-lock brake control module is connected to the SCP communication network. The module comes in two forms. The first type is the standard equipped anti-lock brake system (ABS) with traction control. It controls the brake pressure to the four wheels to keep the vehicle under control while braking.
The second type of ABS is optional and is called dynamic stability control (DSC). This module adds yaw sensors to the package to help in sensing a loss of vehicle control. For additional information, refer to ANTI-LOCK CONTROL-STABILITY ASSIST .
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. .
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 entry. The DDM also communicates with the driver seat module (DSM) to control power seat and mirror memory. For additional information; refer to HANDLES, LOCKS, LATCHES AND ENTRY SYSTEMS .
The DSM is connected to 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 dual automatic temperature control (DATC) module is connected to the SCP communication network. The DATC module controls automatic climate functions that maintain the vehicle at a constant temperature setting. For additional information; refer to CLIMATE CONTROL SYSTEM-GENERAL INFORMATION .
The instrument cluster (also known as a instrument cluster module ICM) is connected to the SCP communication network. The instrument cluster displays information received on the SCP including speedometer, odometer, fuel, and message center warnings. The instrument cluster also controls the passive anti-theft system (PATS). For additional information; refer to INSTRUMENT CLUSTER AND PANEL ILLUMINATION for instrument cluster operation and ANTI-THEFT - PASSIVE for PATS.
The general electronic module (GEM) and rear electronic module (REM) are connected to the SCP communication network. The GEM and REM controls both interior and exterior lighting, active anti-theft functions and warning chimes. For additional information on interior lamps, refer to INTERIOR LIGHTING . For additional information on exterior lighting, refer to EXTERIOR LIGHTING . For additional information on acitve anti-theft, refer to ANTI-THEFT - ACTIVE . For additional information on warning chimes, refer to WARNING DEVICES .
The powertrain control module (PCM) is connected to the SCP communication network. The PCM controls the engine performance, electronic ignition, emission controls, speed control, and on board diagnostics. For additional information; refer to ELECTRONIC ENGINE CONTROLS - 3.0L . For additional information; refer to ELECTRONIC ENGINE CONTROLS - 4.0L .
The vehicle emergency message system (VEMS) module is connected to the SCP communication network. The module allows a user to request emergency assistance (police, ambulance, fire, wrecker) or directions to a desired location at the touch of a button. Also, if any of the vehicle's airbags are deployed while the VEMS system is powered ON, the system automatically issues a call for emergency assistance. For additional information; refer to TELEMATICS .
The steering column lock module (SCLM) is connected to the SCP communication network. The module controls locking of the steering column and is only equipped on vehicles with manual transmissions. For additional information; refer to STEERING COLUMN SWITCHES .
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 voice activated control module (VACM) is connected to the SCP communication network. This allows the user to select functions by giving a voice command the VACM then sends the command information by SCP to the correct module or audio unit.
The electronic throttle control module (ETCM) is connected to the SCP network through the PCM. For additional information, refer to ELECTRONIC ENGINE CONTROLS - 3.0L . For additional information, refer to ELECTRONIC ENGINE CONTROLS - 4.0L .
The adaptive damping control module (ADCM) is connected to the SCP network and controls and monitors the vehicle ride conditions through sensors. The ADCM module adjust the setting of the four dampers fitted to the vehicle to improve the ride quality. For additional information, refer to FRONT SUSPENSION
The navigation computer (NC) is connected SCP network. The NC receives inputs from the GPS antenna and varies other sensors. For additional information, refer to NAVIGATION SYSTEM