Principles of Operation

PRINCIPLES OF OPERATION

The vehicle uses two of the following module communication networks:
- international standards organization (ISO) 9141 communications network.
- controller area network (CAN) communications network.

The vehicle has 2 module communication networks: the CAN network, which is comprised of unshielded twisted pair cable, and the international standards organization (ISO) 9141 communications network, which is a single wire network. Both networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one diagnostic tester to be able to diagnose and control any module on the networks from one connector. The DLC can be found under the instrument panel.

The ISO 9141 communications network does not permit inter-module communication. When the diagnostic tool communicates with the generic electronic module (GEM) on the ISO 9141 communication network, the diagnostic tool must request all information or initiate module commands.

The GEM is the only module on the ISO 9141 communications network.

The ISO 9141 communications network will not function if the wire is shorted to ground or battery voltage. Also, if the GEM loses power or shorts internally, ISO 9141 communications will fail.

The CAN network will remain operational even with the severing of one of the bus wires. If one of the CAN network bus wires becomes shorted to ground or voltage, communications can continue at a reduced level. If any of the termination resistors are lost, communication will not be possible.

Powertrain Control Module (PCM)
The PCM is on the CAN network. The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage.

Restraints Control Module (RCM)
The RCM controls the deployment of the air bags based on sensor input. The RCM is on the CAN network. The RCM communicates with the occupant classification sensor using the CAN network. The occupant classification sensor does not communicate with the diagnostic tool, and is mentioned here as a possible concern should CAN network communication be lost.

Anti-Lock Brake System (ABS)
Module The anti-lock brake system (ABS) module is connected to the CAN network. The ABS module with stability assist is also connected to the CAN network. The ABS module controls the brake pressure to the four wheels to keep the vehicle under control while braking.

Instrument Cluster
The instrument cluster is connected to the CAN network. The instrument cluster displays driver information, including tachometer reading, fuel level, engine coolant level and speed.

Occupant Classification Sensor
The occupant classification sensor is connected to the CAN network. The occupant classification sensor is located in the passenger seat and is used to determine whether or not to deploy an airbag based on the weight detected in the passenger seat. The occupant classification sensor communicates on the CAN network to the RCM only. Diagnosis is carried out through the RCM.

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