Principles of Operation: Notes

WARNING: This page is about a different car, the 2005 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle has three module communication networks: one high speed and one medium speed CAN network, which are comprised of unshielded twisted pair cable, and the international standards organization (ISO) 9141 communications network, which is a single wire network. All three 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 three networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The high speed and medium speed CAN 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 voltage. If any of the termination resistors are lost, communication will not be possible.

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

The ISO 9141 communications network will not function if the wire 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 will fail.