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.

      A0029G5E03

    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. Bus 2


      1. Combination meter assembly

      2. Skid control ECU (brake actuator assembly)

      3. Airbag sensor assembly

      4. Clearance warning ECU assembly*1

      5. Certification ECU (smart key ECU assembly)*2

      6. Air conditioning amplifier assembly

      7. Headlight leveling ECU assembly*3

      8. Steering sensor

      9. ECM

      10. 4WD ECU assembly*4

      11. Power steering ECU assembly

      12. Main body ECU (multiplex network body ECU)

      13. Central gateway ECU (network gateway ECU)

    2. Bus 3


      1. Central gateway ECU (network gateway ECU)

      2. Navigation receiver assembly*5

      3. Radio and display receiver assembly*6

      4. Telematics transceiver*7

    3. Bus 5


      1. Central gateway ECU (network gateway ECU)

      2. Forward recognition camera*8

      3. Millimeter wave radar sensor assembly*8

      4. Driving support ECU assembly*8

      5. Parking assist ECU*9

      6. Blind spot monitor sensor LH*10

      7. Television camera assembly*11

    4. Sub Bus 1


      1. Main body ECU (multiplex network body ECU)

      2. Outer mirror control ECU assembly (for driver side)*13

      3. Outer mirror control ECU assembly (for front passenger side)*13

      4. Position control ECU and switch assembly*13

      5. Multiplex network door ECU*12

    Tech Tips

    *1: w/ Toyota Parking Assist-sensor System

    *2: w/ Smart Entry and Start System

    *3: w/ Automatic Headlight Beam Level Control System

    *4: for AWD

    *5: for Navigation Receiver Type

    *6: for Radio and Display Type

    *7: w/ Telematics Transceiver

    *8: w/ Toyota Safety Sense

    *9: w/ Panoramic View Monitor System

    *10: w/ Blind Spot Monitor System

    *11: w/ Parking Assist Monitor System

    *12: w/ Power Back Door System

    *13: w/ Seat Position Memory System

  4. CIRCUIT DESCRIPTION


    1. The V bus has a termination circuit with a resistor of 60 Ω.

    2. The bus 2, bus 3, bus 5 and sub bus 1 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.

  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