Information Bus Module Communication
MODULE COMMUNICATIONS
Module communications is comprised of the following:
The vehicle has two module communications networks. The powertrain control module is connected to 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 [P/LB]). The Integrated Air Bag Diagnostic Monitor (IABM) and any of the optional modules are connected to the ISO 9141 Link via a single wire (circuit 70 [LB/W]). Both networks can be connected to New Generation STAR (NGS) tester at one connector called the Data Link Connector (DLC). 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 DLC can be found under the instrument panel between the steering column and the radio.
The diagnostic communication network does not permit inter-module communication. When the NGS tester communicates to modules on the diagnostic communication network, the NGS tester must ask for all information; the modules cannot initiate communications.
Fault Tolerance of the SCP
The Standard Corporate Protocol (SCP) 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 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.
Fault Tolerance of the Diagnostic Communications Network
Unlike the SCP, the ISO 9141 Link will not function if the wire is shorted to ground or battery positive voltage (B+). Also, if one of the modules on the diagnostic communication network loses power or shorts internally, communications to that module will fail.
Module Description
The Powertrain Control Module (PCM) is on the multiplex communication network. The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage.
The Integrated Air Bag Diagnostic Monitor (IABM) is on the diagnostic communication network. The IABM controls the deployment of the air bags based on sensor input.
The Generic Electronic Module (GEM) is on the diagnostic communication network. The GEM controls a variety of systems:
^ 4x4.
^ Windshield wipers.
^ Courtesy lamps.
^ One touch down power windows, etc.
^ Warning chimes/lamps.
The Remote Anti-theft Personality (RAP) module is on the diagnostic communication network. The RAP module controls the anti-theft and keyless remote entry of the vehicle.
The 4-Wheel Anti-Lock Brake System (4WABS) module is on the diagnostic communication network. The 4WABS module controls the brake pressure to the four wheels to keep the vehicle under control while braking.
The Electronic Automatic Temperature Control (EATC) module is on the diagnostic communication network. The EATC module controls automatic climate functions that maintain the vehicle cabin at a constant temperature setting.
The Automatic Ride Control (ARC) system is a computer controlled suspension system. The front and rear shock absorber contains an integrated air spring. The front and rear air springs provide automatic load leveling and a ride adjustment with a total span of 50 mm (2 in).
The electronic steering sensor is mounted on the steering column inside the passenger compartment. The electronic steering sensor monitors the direction of turn and speed of the steering column rotation to allow an air pressure differential in the front and rear air springs during vehicle lean in a turn.
The ARC module programming has a time delay compensation for normal suspension travel over rough roads so the ARC system will not attempt to continuously adjust vehicle ride height.
There is one height sensors mounted in the front and rear of the vehicle. The height sensors have a total travel range of 80 mm (3 in).