Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 3 module communication networks: standard corporate protocol (SCP), which is an unshielded twisted pair cable data bus plus and data bus minus, the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communication network, a single wire network, and the international standards organization (ISO) 9141 communication network, which is a single wire network. All 3 networks are connected to the data link connector (DLC) C251. This makes diagnosis and testing of these systems easier by allowing 1 diagnostic tester 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 radio.

The SCP communication network remains operational even with the severing of 1 of the bus wires. Communications can also continue if 1 of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.

The ISO 9141 communication network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communications. The ISO 9141 communication network does not function if the wire is shorted to ground or battery voltage. Also, if 1 of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module fail.

The UBP communication network does not function if the wire is shorted to ground or voltage. The UBP communication network allows intermodule communication.