CAN COMMUNICATION SYSTEM(for LHD) SYSTEM DESCRIPTION

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.
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 V bus has termination circuits with two resistors of 60 Ω, and the bus 2, bus 3, bus 4, bus 5, sub bus 1 and sub bus 15 each have termination circuits with two resistors of 120 Ω.
5. The CAN communication system is composed of 6 buses.
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.
ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM
1. V Bus
  1. Central gateway ECU
  2. DLC3
2. Bus 2
  1. ECM
  2. Parking brake ECU assembly
  3. Main body ECU (multiplex network body ECU)
  4. Skid control ECU assembly
  5. Steering angle sensor
  6. Airbag sensor assembly
  7. Yaw rate sensor
  8. Certification ECU (smart key ECU assembly)
  9. Air conditioning amplifier assembly
  10. Power steering ECU assembly
  11. Front steering control ECU*1
  12. Central gateway ECU
  13. Combination meter mirror ECU
  14. Combination meter assembly*2
  15. Power management control ECU
    - *1: w/ Variable Gear Ratio Steering System
    - *2: w/ Headup Display System
3. Bus 3
  1. Central gateway ECU
  2. Multi-media module receiver assembly
  3. Telematics transceiver*
    - *: w/ Telematics Transceiver
4. Bus 4
  1. Skid control ECU assembly
  2. Absorber control ECU*1
  3. Power steering ECU assembly
  4. Front steering control ECU*2
  5. Central gateway ECU
  6. Driving support ECU assembly*3
  7. Rear steering control ECU*4
    - *1: w/ Adaptive Variable Suspension System
    - *2: w/ Variable Gear Ratio Steering System
    - *3: w/ Pre-crash Safety System
    - *4: w/ Dynamic Rear Steering System
5. Bus 5
  1. Central gateway ECU
  2. Headlight ECU sub-assembly LH
  3. Power management control ECU
  4. Absorber control ECU*1
  5. Driving support ECU assembly*2
  6. Forward recognition camera*2
  7. Millimeter wave radar sensor assembly*2
  8. Clearance warning ECU assembly*3
  9. Blind spot monitor sensor RH*4
    - *1: w/ Adaptive Variable Suspension System
    - *2: w/ Pre-crash Safety System
    - *3: w/ LEXUS Parking Assist-sensor System
    - *4: w/ Blind Spot Monitor System
6. Sub Bus 1
  1. Main body ECU (multiplex network body ECU)
  2. Luggage closer motor assembly*1
  3. Multiplex network door ECU*2
  4. Position control ECU assembly LH*3
  5. Power seat switch assembly*4
  6. Position control ECU assembly RH*5
  7. Front multiplex network door ECU LH
  8. Front multiplex network door ECU RH
  9. Multiplex tilt and telescopic ECU
    - *1: w/ Power Trunk Lid System
    - *2: w/o Power Trunk Lid System
    - *3: except Standard Seat Type
    - *4: for Standard Seat Type
    - *5: for Luxury Seat Type
7. Sub Bus 15
  1. ECM
  2. Skid control ECU assembly
  3. Power management control ECU
CIRCUIT DESCRIPTION
1. The V bus has a termination circuit with a resistor of 60 Ω.
2. The bus 2, bus 3, bus 4, bus 5, sub bus 1 and sub bus 15 each have termination circuits with two resistors of 120 Ω.
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 main lines. If there is any trouble in the DLC3 or the DLC3 main lines, ECUs on the CAN cannot output DTCs to the GTS.
DIAGNOSTIC TROUBLE CODES FOR CAN COMMUNICATION SYSTEM

Tech Tips

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