Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 3 module communications networks:
- high speed controller area network (CAN)
- medium speed CAN
- international standards organization (ISO) 9141 communications network

All 3 networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing 1 diagnostic tool to be able to diagnose and control any module on the 3 networks from 1 connector. The DLC can be found under the instrument panel between the steering column and the audio unit.

Both the high speed and medium speed CAN consist of an unshielded twisted pair cable, data plus circuit and data minus circuit. The CAN is not designed to operate under single point fault conditions. If either circuit is shorted to voltage or the CAN data plus is shorted to ground, module-to-module and module-to-tester communication is not possible. If the CAN data minus is shorted to ground or an open exists on either bus line, module-to-module and module-to-tester communication is marginal at best. The CAN bus may remain operational when one of the two termination resistors are not present. If there are issues with the CAN, there may be missing functionality and problems connecting with a diagnostic tool.

High Speed Controller Area Network (CAN)
The high speed CAN has an unshielded twisted pair cable, data plus circuit 1908 (WH) and data minus circuit 1909 (BK). The high speed CAN is a high speed communications network used for the anti-lock brake system (ABS) module, the differential electronic module (DEM) (if equipped), the transmission control module (TCM) - 6-speed transaxle, TCM - continuously variable transaxle (CVT), the instrument cluster, the powertrain control module (PCM) and the restraint control module (RCM) communication.

On the high speed CAN, there are 2 terminating modules which are composed of the PCM and the instrument cluster.

Medium Speed Controller Area Network (CAN)
The medium speed CAN has an unshielded twisted pair cable, data plus circuit 2180 (WH/BK) and data minus circuit 2181 (BK/YE). The medium speed CAN is used for the audio unit or audio navigation unit (if equipped), the driver seat module (DSM) (if equipped), the dual automatic temperature control (DATC) module (if equipped), the digital versatile disc (DVD) player (if equipped), the instrument cluster, and the smart junction box (SJB) communications.

On the medium speed CAN, there are 2 terminating modules which are composed of the smart junction box (SJB) and the instrument cluster.

International Standards Organization (ISO) 9141 Communications Network
The ISO 9141 communications network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communications network, the diagnostic tool must ask for all information; the modules cannot initiate communications. The ISO 9141 communications network does not function if the circuit is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module fail.

The ISO 9141 communication network is a single wire network. The ISO 9141 communications network communicates with the parking aid module (PAM).