Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 3 module communications networks: the standard corporate protocol (SCP) communications network, which is an unshielded twisted pair cable, data bus plus, circuit 914 (TN/OG), and data bus minus; circuit 915 (PK/LB), the single wire, circuit 693 (OG), universal asynchronous receiver transmitter (UART) based protocol (UBP) communications network; and the international standards organization (ISO) 9141 communications network, which is also a single wire communications network, circuit 70 (LB/WH). All 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 driver door near the parking brake lever.

The SCP communications network remains operational even with the severing of one of the communications network circuits. Communications also continue if one of the 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 communications. 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 wire is shorted to ground or voltage. The UBP communications network allows intermodule communications.