CAN COMMUNICATION SYSTEM(w/o Central Gateway ECU) 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 CAN has two resistors of 120 Ω which are necessary to enable communication.
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. Combination meter assembly
  2. Certification ECU (smart key ECU assembly)*1
  3. Steering sensor (spiral cable with sensor sub-assembly)*2
  4. Radio and display receiver assembly*3
  5. Airbag sensor assembly
  6. Power steering ECU assembly
  7. Air conditioning amplifier assembly*4
  8. Clearance warning ECU assembly*5
  9. Engine stop and start ECU*6
  10. Brake actuator assembly
  11. Main body ECU (multiplex network body ECU)
  12. Headlight leveling ECU assembly*7
  13. Headlight swivel ECU assembly*8
  14. ECM
  15. Pre-crash safety city sensor*9
  16. Telematics transceiver*10
Tech Tips
- *1: w/ Entry and Start System
- *2: w/ VSC
- *3: for Radio and Display Type
- *4: w/ Air Conditioning System
- *5: w/ Simple Intelligent Parking Assist System
- *6: w/ Stop and Start System
- *7: for Sedan with Automatic Headlight Beam Level Control System
- *8: except Sedan with Automatic Headlight Beam Level Control System
- *9: w/ Toyota Safety Sense
- *10: w/ Manual (SOS) Switch
CIRCUIT DESCRIPTION
1. The V bus has 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.
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.
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