Principles of Operation

The vehicle has 4 module communication networks: the first 2 are the high speed and medium speed CAN networks, which are comprised of an unshielded twisted pair cable. The third network is the international standards organization (ISO) 9141 communication network, which is a single wire network. The fourth network is the audio control protocol (ACP) network, which consists of a twisted pair cable and a control line. The first 3 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 3 networks from one connector. The DLC can be found under the instrument panel between the steering column and the audio unit.

The high speed and medium speed CAN networks can remain operational at a reduced level even with an open in the system. If one of the bus wires becomes shorted to ground or shorted to voltage, communication over the network may not be possible.

The ISO 9141 communication network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communications.

The ISO 9141 communication network does not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module may fail.