CAN COMMUNICATION SYSTEM 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.

      A01MT4CE11

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

  2. DEFINITION OF TERMS


    1. Main bus


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

    2. Branch


      1. A branch is a wire harness which diverges from the main bus 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 lines. They are called terminating resistors. These resistors allow the changes of the voltage differential between the CAN bus lines 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 THROUGH CAN COMMUNICATION SYSTEM


    1. V Bus


      1. ECM

      2. Network gateway ECU*1

      3. Main body ECU (multiplex network body ECU)

      4. Skid control ECU assembly

      5. Power management control ECU

      6. Air conditioning amplifier assembly

      7. Steering sensor

      8. Headlight leveling ECU assembly

      9. Certification ECU (smart key ECU assembly)

      10. Airbag sensor assembly

      11. Yaw rate sensor

      12. Power steering ECU assembly

      13. Combination meter assembly

      14. Radio receiver assembly

      15. Stereo component equalizer assembly*2

    2. Sub Bus 1*3*4


      1. Main body ECU (multiplex network body ECU)

      2. Outer mirror control ECU assembly (for driver side)*3

      3. Outer mirror control ECU assembly (for front passenger side)*3

      4. Front power seat switch LH*3*10

      5. Front power seat switch RH*3*11

      6. Multiplex tilt and telescopic ECU*4

    3. Sub Bus 2*1


      1. Network gateway ECU

      2. Driving support ECU assembly*5

      3. Absorber control ECU*6

      4. Clearance warning ECU assembly*7

      5. Blind spot monitor sensor LH*8

      6. Lane departure warning camera*9

      7. Power management control ECU

    4. Sub Bus 13*5


      1. Driving support ECU assembly

      2. Millimeter wave radar sensor assembly

    5. Sub Bus 15


      1. Power management control ECU

      2. ECM

      3. Skid control ECU assembly

    Tech Tips

    *1: w/ Network gateway ECU

    *2: w/ ASC system

    *3: w/ Seat position memory system

    *4: w/ Power tilt and power telescopic system

    *5: w/ Pre-crash safety system

    *6: w/ AVS system

    *7: w/ LEXUS parking assist-sensor system

    *8: w/ Blind spot monitor system

    *9: w/ Lane departure alert system

    *10: for LHD

    *11: for RHD

  4. CIRCUIT DESCRIPTION


    1. The V bus, sub bus 1, sub bus 2, sub bus 13 and sub bus 15 each have termination circuits with two resistors of 120 Ω.

  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 lines. If there is a malfunction in the DLC3 or the DLC3 branch lines, ECUs on the CAN cannot output DTCs to the GTS.

    2. Malfunctions in the CAN V bus (communication lines) can be checked by measuring the resistance between terminals of the DLC3. However, an open circuit in a branch line other than the DLC3 branch lines cannot be checked from the DLC3 (except for the DLC3 branch lines).

      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 connectors connected to the CAN junction connector which has an earth terminal are the same. The connectors connected to the CAN junction connector can be distinguished by the colors of the bus lines and the connecting side of the junction connector.

      Tech Tips

      See Terminals of ECU for bus line color or the shape of connectors.

      Click here