Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 4 communications networks: the controller area network (CAN), the standard corporate protocol (SCP) communications network, which is an unshielded twisted pair cable data communications network plus and data communications network minus, the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communications network, a single circuit communications network and the international standards organization (ISO) 9141 communications network, which is a single circuit communications network. All 4 communications networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one smart tester to be able to diagnose and control any module on the 2 communications networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The CAN is a high speed communications network used for powertrain communication. The CAN remains operational even with the severing of one of the CAN circuits. Communications also continue if one of the CAN circuits are shorted to ground or voltage, or if some but not all termination resistors are lost.

The SCP communications network remains operational even with the severing of one of the SCP communications network circuits. Communications also continue if one of the SCP communications network circuits are shorted to ground or voltage, or if some but not all termination resistors are lost.

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 UBP communications network does not function if the circuit is shorted to ground or voltage. The UBP communications network is different from the ISO 9141 communications network in that it allows intermodule communication.