Module Communications Network

The vehicle has two separate module communication networks. 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]) and the International Standards Organization (ISO) 9141 Network 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 ISO 9141 communication network does not permit inter-module communication. When the NGS tester communicates to modules on the ISO 9141 communication network, the NGS tester must ask for all information; the modules cannot initiate communications.

The 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.

Unlike the SCP, the ISO 9141 communication network will not function if the wire is shorted to ground or battery positive voltage (B+). Also, if one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module will fail.

There are three modules linked to the SCP communication network and six modules linked to the ISO 9141 communication network.