Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 3 module communications networks:
- controller area network (CAN)
- universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communications network
- international standards organization (ISO) 9141 communications network

The CAN has an unshielded twisted pair cable, data bus plus, circuit 3126 (TN/YE) and data bus minus, circuit 3125 (RD/YE). The UBP communications network uses a single wire network circuit 693 (OG), as does the ISO 9141 communications network, which is a single wire 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 tool to be able to diagnose and control any module on the 3 networks from one connector. The DLC can be found just above the parking brake release handle.

The CAN permits inter-module communications between the DLC, powertrain control module (PCM), instrument cluster, electronic automatic temperature control (EATC) module, tire pressure monitoring system module, and the anti-lock brake system (ABS) modules. When the diagnostic tool communicates to modules on the CAN, the diagnostic tool must request all information or initiate module commands.

The CAN does not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the CAN loses power or shorts internally, communications to that module fail. Both the PCM and the instrument cluster have internal termination resistors required for correct communications network operation.

The UBP communications network allows inter-module communications. The UBP communications network does not function if the wire is shorted to ground or voltage. If one of the modules on the UBP communications network loses power or shorts internally, communications to that module fail.

The ISO 9141 communications network does not permit inter-module 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 wire is shorted to ground or voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module fail.