System Description [06/2014 - 10/2016]

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.
   Fig 1: Controller Area Network (CAN) System Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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.

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.

1. V Bus
   1. ECM
   2. Network gateway ECU*1
   3. Option connector (bus buffer ECU)*2
   4. Main body ECU (multiplex network body ECU)
   5. Skid control ECU (brake actuator assembly)
   6. Telematics transceiver*3
   7. Air conditioning amplifier assembly
   8. Steering sensor
   9. Headlight leveling ECU assembly
   10. Certification ECU (smart key ECU assembly)
   11. DLC3
   12. Airbag sensor assembly
   13. Yaw rate sensor
   14. Power steering ECU assembly
   15. Radio receiver assembly
   16. Combination meter assembly
   17. Front steering control ECU*4
2. Sub Bus 1*5*6*7
   1. Main body ECU (multiplex network body ECU)
   2. Outer mirror control ECU assembly (for driver side)*5
   3. Outer mirror control ECU assembly (for front passenger side)*5
   4. Front power seat switch LH*5
   5. Multiplex tilt and telescopic ECU*6
   6. Rear television camera assembly*7
3. Sub Bus 2*1
   1. Network gateway ECU
   2. Driving support ECU assembly*8
   3. 4WD ECU assembly*9
   4. Absorber control ECU*10
   5. Clearance warning ECU assembly*11
   6. Blind spot monitor sensor LH*12
   7. Lane departure warning camera*13
   8. Option connector (bus buffer ECU)*14
4. V3 Bus*4
   1. Power steering ECU assembly
   2. Absorber control ECU
   3. Front steering control ECU
   4. Skid control ECU (brake actuator assembly)
5. Sub Bus 13*8
   1. Driving support ECU assembly
   2. Millimeter wave radar sensor assembly

HINT: 

*1: w/ Network Gateway ECU

*2: w/o Network Gateway ECU

*3: for Lexus Enform Remote Compatible Type

*4: w/ VGRS System

*5: w/ Seat Position Memory System

*6: w/ Power Tilt and Power Telescopic System

*7: w/ Parking Assist Monitor System

*8: w/ Pre-collision System

*9: for AWD

*10: w/ AVS System

*11: w/ Intuitive Parking Assist System

*12: w/ Blind Spot Monitor System

*13: w/ Lane Departure Alert System

*14: w/ Option Connector

1. The V bus, sub bus 1, sub bus 2, V3 bus and sub bus 13 each have termination circuits with two resistors of 120 Ω.

1. DTCs for the CAN communication system can be checked using the Techstream. 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 Techstream.
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.

HINT: 

See Diagnosis System.

Refer to DIAGNOSIS SYSTEM [06/2014 - 08/2015] , or refer to DIAGNOSIS SYSTEM [08/2015 - 10/2016]

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.

   HINT: 

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

   Refer to TERMINALS OF ECU [06/2014 - 08/2015] , or refer to TERMINALS OF ECU [08/2015 - 10/2016]