Principles of Operation

PRINCIPLES OF OPERATION

The vehicle uses the following module communication networks:
- controller area network (CAN) communications network
- international standards organization (ISO) 9141 communications network

The CAN is comprised of unshielded twisted pair cable, and the ISO 9141 communications network is a single wire network. Both 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 networks from one connector. The DLC can be found under the instrument panel.

Controller Area Network (CAN)
The CAN is not designed to operate under single point fault conditions. If either circuit is shorted to voltage or CAN data plus is shorted to ground, module-to-module and module-to-tester communication is not possible. If 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.

International Standards Organization (ISO) 9141 Communications Network
The ISO 9141 communications network does not permit inter-module communication. When the diagnostic tool communicates with the generic electronic module (GEM) on the ISO 9141 communication network, the diagnostic tool must request all information or initiate module commands.

The ISO 9141 communications network does not function if the wire is shorted to ground or battery voltage. Also, if the GEM loses power or shorts internally, ISO 9141 communications will fail.

The GEM is the only module on the ISO 9141 communications network.