CAN COMMUNICATION SYSTEM SYSTEM DESCRIPTION


  1. BRIEF DESCRIPTION


    1. Two different types of CAN buses are used. The CAN buses are classified into two types based on typical communication speed. The HS-CAN bus is a high speed communication bus that is used for powertrain, chassis, and some body electrical communication. The HS-CAN bus is referred to as "CAN No. 1 bus". It operates at speeds of approximately 500 kbps. Terminating resistors for the CAN No. 1 bus are located in the combination meter and ECM. The resistance of the CAN No. 2 bus cannot be measured from the DLC3 connector. The MS-CAN bus is a medium speed communication bus that is used for body electrical communication. The MS-CAN bus is referred to as "MS bus" and it operates at speeds of approximately 250 kbps. Terminating resistors for the MS-CAN bus are located in the main body ECU and the certification ECU (or the CAN junction connector RR). The resistance of the MS-CAN bus cannot be measured from the DLC3 connector. Communication between these networks is handled via the main body ECU (for the CAN MS bus), which acts as a gateway.

    2. The CAN (Control Area Network) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed and the ability to detect malfunctions.

    3. By pairing the CANH and CANL bus wires, the CAN performs communication based on differential voltage.

    4. Many ECUs (sensors) installed on the vehicle operate by sharing information and communicating with each other.

    5. The CAN has two resistors of 120 Ω which are necessary to communicate with the main bus wire.

  2. DEFINITION OF TERMS


    1. Main bus wire


      1. The main bus wire is a wire harness between the two terminating resistors on the bus (communication wire). This is the main bus in the CAN communication system.

    2. Branch wire


      1. The branch wire is a wire harness which diverges from the main bus wire to an ECU or sensor.

    3. Terminating resistors


      1. Two resistors of 120 Ω are installed in parallel across the ends of the CAN main bus wire. They are called terminating resistors. These resistors allow the changes of the voltage differential between the CAN bus wires to be accurately judged. To allow proper function of CAN communication, it is necessary to have both terminating resistors installed. Since the two resistors are installed in parallel, a measurement of resistance between the two CAN bus wires should produce a reading of approximately 60 Ω.

  3. ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM


    1. ECM

    2. Combination meter

    3. Skid control ECU

    4. Yaw rate sensor

    5. Steering angle sensor

    6. Air conditioning amplifier

    7. Power steering ECU

    8. Center airbag sensor assembly

    9. Main body ECU

    10. Television camera ECU (w/ Parking assist monitor system)

    11. Certification ECU (w/ Smart entry and start system)

    12. Back door ECU (w/ Power back door system)

  4. DIAGNOSTIC CODE FOR CAN COMMUNICATION SYSTEM


    1. DTCs for the CAN communication system are as follows: U0073, U0100, U0123, U0124, U0126, U0129, U0230*2, U0327*1, U1002*1 *2and B1499.

      *1: w/ Smart entry and start system

      *2: w/ Power back door system

  5. TROUBLESHOOTING REMARKS


    1. DTCs for the CAN communication system can be checked using the intelligent tester. The DLC3 is connected to the CAN communication system, but no DTCs exist regarding problems in the DLC3 or the DLC3 branch wires. If there is trouble in the DLC3 or the DLC3 branch wires, ECUs on the CAN network cannot output codes to the intelligent tester.

    2. Trouble in the CAN buses (communication wires) can be checked by measuring the resistance between terminals of the DLC3. However, an open circuit in a branch wire other than the DLC3 branch wires cannot be checked from the DLC3.

      Note

      Do not insert the tester probes directly into the DLC3. Be sure to use service wires.

  6. HOW TO DISTINGUISH THE CAN JUNCTION CONNECTOR


    1. In the CAN communication system, the shape of all connectors connected to the CAN junction connector is the same. The connectors connected to the CAN Junction connector can be distinguished by the colors of the bus wire and the connecting side of the junction connector.

      Tech Tips

      See "TERMINALS OF ECU" Click herefor bus wire color or the type of connecting surface.