Principles Of Operation

The diagnostic tool connects to the 3 communications networks through the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one diagnostic tool to be able to diagnose and control any module on the 3 communications networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The controller area network (CAN) permits inter-module communications between the DLC, the powertrain control module (PCM), the fire suppression module (FSM), and the anti-lock brake system (ABS) module. When the diagnostic tool communicates to modules on the CAN, the diagnostic tool must request all information or initiate module commands.

The CAN does not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the CAN loses power or shorts internally, communications to that module fail. The PCM has an internal termination resistor required for correct communications network operation.

The international standards organization (ISO) 9141 communications network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communications network, the diagnostic tool must request all information or initiate module commands.

The ISO 9141 communications network will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module will fail.

The standard corporate protocol (SCP) communications network remains operational even with the severing of one of the bus wires. Communications also continues if one of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.

The restraints control module (RCM) is connected to the ISO 9141 communications network. The RCM controls the deployment of the air bags based on sensor input. For additional information, refer to SUPPLEMENTAL RESTRAINT SYSTEM .

The driver door module (DDM) is connected to the ISO 9141 communications network. The module controls many functions including power windows, power locks, and keyless remote entry. For additional information, refer to HANDLES, LOCKS, LATCHES AND ENTRY SYSTEMS .

The lighting control module (LCM) is connected to the ISO 9141 communications network. The LCM controls both interior and exterior lighting, anti-theft functions, and warning chimes. For additional information on interior lighting, refer to INTERIOR LIGHTING . For additional information on exterior lighting, refer to EXTERIOR LIGHTING . For additional information on anti-theft, refer to ANTI-THEFT . For additional information on warning chimes, refer to WARNING DEVICES .

The electronic automatic temperature control (EATC) module is connected to the SCP communications network. The EATC 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 PCM is connected to the CAN and the SCP communications network. The PCM controls the engine performance, electronic ignition, emission controls, and on-board diagnostics. For additional information, refer to ELECTRONIC ENGINE CONTROLS . The passive anti-theft system (PATS) is integrated into the PCM. The PCM controls the PATS functions as well as illumination of the anti-theft indicator. The illumination command is sent from the PCM through the SCP communications network to the instrument cluster, which in turn sends power to the anti-theft indicator. The PCM stores the ignition key codes and controls engine disable. For additional PATS information, refer to ANTI-THEFT .

The ABS module is connected to the CAN. The ABS module controls the brake pressure to the 4 wheels to keep the vehicle under control while braking. For additional information, refer to ANTI-LOCK CONTROL .

The rear air suspension module (RASM) is connected to the SCP communications network. The RASM controls the rear ride height. Refer to VEHICLE DYNAMIC SUSPENSION .

The fire suppression module (FSM) is connected to the CAN and the ISO 9141 communications network. The fire suppression system is designed to help reduce the risk of fire in high speed rear impacts. The fire suppression system deploys chemicals designed to suppress the spread of fire or potentially extinguish a fire, thereby providing more time for occupants to escape from a crashed vehicle. Refer to FIRE SUPPRESSION SYSTEM .