CAN COMMUNICATION SYSTEM 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 to the vehicle operate by sharing information and communicating with each other.
4. The V bus has termination circuits with a resistor of 60 Ω, and the bus 2, bus 3, bus 5, sub bus 1 and sub bus 15 each have termination circuits with two resistors of 120 Ω.
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 (network gateway ECU)
2. Bus 2
  1. Central gateway ECU (network gateway ECU)
  2. ECM
  3. Main body ECU (multiplex network body ECU)
  4. Skid control ECU assembly
  5. Hybrid vehicle control ECU assembly
  6. Air conditioning amplifier assembly
  7. Steering sensor
  8. Headlight leveling ECU assembly*1
  9. Certification ECU (smart key ECU assembly)
  10. Airbag ECU assembly
  11. Yaw rate sensor
  12. Power steering ECU assembly
  13. Combination meter assembly
  14. Stereo component equalizer assembly*2
3. Bus 3
  1. Central gateway ECU (network gateway ECU)
  2. Radio receiver assembly
4. Bus 5
  1. Central gateway ECU (network gateway ECU)
  2. Hybrid vehicle control ECU assembly
  3. Driving support ECU assembly*3
  4. Forward recognition camera*3
  5. Millimeter wave radar sensor assembly*3
  6. Absorber control ECU*4
  7. Clearance warning ECU assembly*5
  8. Blind spot monitor sensor LH*6
  9. Rear television camera assembly*7
5. Sub Bus 1
  1. Main body ECU (multiplex network body ECU)
  2. Outer mirror control ECU assembly (for driver side)*8
  3. Outer mirror control ECU assembly (for front passenger side)*8
  4. Position control ECU and switch assembly LH
  5. Position control ECU and switch assembly RH
  6. Multiplex tilt and telescopic ECU*9
  7. Headlight ECU sub-assembly*10
6. Sub Bus 15
  1. Hybrid vehicle control ECU assembly
  2. ECM
  3. Skid control ECU assembly
Tech Tips

*1: for Single Beam Headlight

*2: w/ ASC System

*3: w/ Lexus Safety System +

*4: w/ AVS System

*5: w/ LEXUS Parking Assist-sensor System

*6: w/ Blind Spot Monitor System

*7: w/ Parking Assist Monitor System

*8: w/ Seat Position Memory System

*9: w/ Power Tilt and Power Telescopic System

*10: for Triple Beam Headlight
CIRCUIT DESCRIPTION
1. The V bus has a termination circuit with a resistor of 60 Ω.
2. The bus 2, bus 3, 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 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.
DIAGNOSTIC TROUBLE CODES FOR CAN COMMUNICATION SYSTEM

Tech Tips

See Diagnosis System.

Click here
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