Principles of Operation (How Does It Work?)

The vehicle uses two of the following module communication networks:
- international standards organization (ISO) 9141 communications network.
- standard corporate protocol (SCP) communications network (if equipped).
- high speed controller area network (CAN) communications network (2.3L only).

The diagnostic tool connects to the 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 three networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The ISO 9141 communications network does not permit inter-module communication. When the diagnostic tool communicates to modules on the ISO 9141 communication 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 SCP communications network will remain operational even with the severing of one of the bus wires. Communications will also continue if one of the bus wires is shorted to ground or voltage, or if some, but not all, termination resistors are lost.

Used only on the 2.3L and 2.0L SVT vehicles, the high speed CAN communications network permits inter-module communication between the DLC, PCM and the instrument cluster (2.3L only). When the diagnostic tool communicates to modules on the high speed CAN communication network, the diagnostic tool must request all information or initiate module commands.

The high speed CAN communications network will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the high speed CAN communications network loses power or shorts internally, communications to that module will fail. Both the PCM and the instrument cluster have internal termination resistors required for correct network communications operation.

The powertrain control module (PCM) is on either the high speed CAN or the SCP communication network. The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage.

The restraints control module (RCM) controls the deployment of the air bags based on sensor input. The RCM is on the ISO 9141 network.

The anti-lock brake system (ABS) module is connected to the IS0 9141 communication network. The ABS module with stability assist 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.

The instrument cluster is connected to either the high speed CAN or the SCP communication network. The instrument cluster displays driver information, including tachometer reading, fuel level, engine coolant level and speed.

The generic electronic module (GEM) is on the ISO 9141 communications network. The GEM controls a variety of systems:
- windshield wipers
- courtesy lamps
- warning chimes
- interior lamps
- exterior lamps
- power windows
- security