CAN COMMUNICATION SYSTEM(for LHD) SYSTEM DESCRIPTION


  1. BRIEF DESCRIPTION


    1. The Controller Area Network (CAN) 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.

      A000094E09

    2. Using the CANH and CANL bus wires as a pair, CAN communication is performed using a voltage differential. (A base voltage is applied to the pair of wires and a voltage differential is created when communicating.)

    3. Many ECUs or sensors installed on the vehicle operate by sharing information and communicating with each other.

    4. The CAN has two resistors of 120 Ω which are necessary to enable communication.

    5. Control system CAN is composed of 5 buses.

  2. DEFINITION OF TERMS


    1. CAN main wire


      1. The CAN main wire is a wire harness between the 2 termination circuits on the bus (communication wire). This is the main bus in the CAN communication system.

    2. CAN branch wire


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

    3. Termination circuits


      1. Two resistors of 120 Ω are installed in parallel across the ends of the CAN main bus wires. 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, this results in a measurement of approximately 60 Ω.

  3. ECUS OR SENSORS WHICH COMMUNICATE VIA CAN COMMUNICATION SYSTEM


    1. V Bus


      1. ECM

      2. Hybrid vehicle control ECU

      3. Brake booster with master cylinder assembly (skid control ECU)

      4. Air conditioning amplifier assembly

      5. Power steering ECU assembly

      6. Spiral with sensor cable sub-assembly (steering angle sensor)

      7. Main body ECU (multiplex network body ECU)

      8. Combination meter assembly

      9. Certification ECU (smart key ECU assembly)

      10. Airbag ECU assembly

      11. Parking brake ECU assembly

      12. Radio receiver assembly*1

      13. Stereo component equalizer assembly*2

      14. Telematics transceiver*3

      15. Bus buffer ECU


        • *1: w/ Navigation System or Audio and Visual System

        • *2: w/ ASC System

        • *3: w/ Emergency Call Switch

    2. Sub Bus 1


      1. Main body ECU (multiplex network body ECU)

      2. Multiplex tilt and telescopic ECU*1

      3. Outer mirror control ECU assembly RH*2

      4. Outer mirror control ECU assembly LH*2

      5. Front power seat switch LH*2

      6. Headlight light control ECU sub-assembly LH

      7. Multiplex network door ECU*3


        • *1: for Power Tilt and Power Telescopic Steering Column

        • *2: w/ Memory

        • *3: w/ Power Back Door System

    3. Sub Bus 11


      1. Hybrid vehicle control ECU

      2. Clearance warning ECU assembly*1

      3. Driving support ECU assembly*2

      4. Lane departure warning camera*3

      5. Parking assist ECU*4

      6. Blind spot monitor sensor LH*5

      7. Absorber control ECU*6


        • *1: w/ LEXUS Parking Assist-sensor System

        • *2: w/ Pre-crash Safety System

        • *3: w/ Lane Departure Alert System

        • *4: w/ Panoramic View Monitor System

        • *5: w/ Blind Spot Monitor System

        • *6: w/ Adaptive Variable Suspension System

    4. Sub Bus 15


      1. ECM

      2. Hybrid vehicle control ECU

      3. Brake booster with master cylinder assembly (skid control ECU)

    5. Local Bus (w/ Pre-crash Safety System)


      1. Driving support ECU assembly

      2. Millimeter wave radar sensor assembly

  4. CIRCUIT DESCRIPTION


    1. The V bus, sub bus 1, sub bus 11, sub bus 15 and local bus each have termination circuits with a resistance of 120 Ω x 2. High speed communication at 500 kbps and 250 kbps is possible.

  5. TROUBLESHOOTING REMARKS


    1. DTCs for the CAN communication system can be checked using the GTS. 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 a malfunction in the DLC3 or the DLC3 branch wires, ECUs on the CAN cannot output DTCs to the GTS.

    2. Malfunctions in the CAN V bus (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 (except for the DLC3 branch wires).

      Note

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

  6. DIAGNOSTIC TROUBLE CODES FOR CAN COMMUNICATION SYSTEM

    Tech Tips

    See Diagnosis System

    Click here

  7. HOW TO DISTINGUISH CONNECTOR OF 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 connector.

      Tech Tips

      Refer to "Terminals of ECU" for the bus wire color or the connecting side of the connector.

      Click here