Information Bus: Description and Operation

The vehicle has two module communications networks. The Powertrain Control Module (PCM) is connected to the Standard Corporate Protocol (SCP) (Data Bus Plus, circuit 131 [W/BL] and Data Bus Minus, circuit 132 [BK/BL]). The Remote Anti-theft Personality (RAP) module and any of the optional modules are connected to the ISO 9141 Link via a single wire (circuit 529 [O/BL]). 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 either network from one connector. The DLC is located under the instrument panel between the steering column and the radio.

The diagnostic communication network does not permit inter-module communication. When NGS Tester communicates to modules on the diagnostic communication network, NGS Tester must ask for all information; the modules cannot initiate communications.

The SCP will remain operational even when one of the bus wires is severed. Communication 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 network bus interface circuits.

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, communication to that module will fail.

The PCM is on the SCP network. The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage.

The air bag diagnostic monitor is on the ISO 9141 Link network. The air bag diagnostic monitor controls the deployment of the air bags based on sensor input.

The RAP is on the ISO 9141 Link network. The RAP module controls the remote entry, trunk release and panic alarm from the keyless entry remote.

The anti-lock brake control module is on the ISO 9141 Link network. The module controls the brake pressure to the four wheels to keep the vehicle under control while braking.