System Description

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

BRIEF DESCRIPTION
1. The CAN (Controller Area Network) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed (500 kbps) and the ability to detect malfunctions.
2. By pairing the CANH and CANL bus lines, the CAN performs communication based on differential voltage.
3. Many ECUs (sensors) installed on the vehicle operate by sharing information and communicating with each other.
4. The CAN has 2 terminating resistors of 120 Ω which are necessary to communicate with the main bus line.
DEFINITION OF TERMS
1. Main bus line
  1. The main bus line is a wire harness between the 2 terminating resistors on the bus (communication line). This is the main bus in the CAN communication system.
2. Sub bus line
  1. The sub bus line is a wire harness which diverges from the main bus line 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 wires. They are called terminating resistors. These resistors allow the changes of the voltage differential between the CAN bus wires 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, a measurement of resistance between the two CAN bus wires should produce a reading of approximately 60 Ω.
ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM
1. Skid Control ECU
2. Yaw Rate Sensor
3. Steering Angle Sensor
4. ECM
5. Network Gateway ECU
6. Navigation ECU*1
7. Center Airbag Sensor Assembly
  *1: w/ Navigation system
DIAGNOSTIC CODE FOR CAN COMMUNICATION SYSTEM
1. DTCs for the CAN communication system are as follows: U0073, U0100, U0123, U0124 and U0126.
  NOTE:
  U0001 are displayed on the Techstream "Communication Malfunction DTC". Refer to DIAGNOSIS SYSTEM screen, but they are not DTCs in the CAN communication system. Refer to the appropriate troubleshooting article of each system.
REMARK FOR TROUBLESHOOTING
1. Trouble in the CAN bus (communication line) can be checked from the DLC3 (except when there is a wire break other than in the sub bus line of the DLC3).
  NOTE:
  Do not insert the tester probes directly into the DLC3 connector. Be sure to use service wires.
2. DTCs regarding the CAN communication system can be checked using the Techstream.
3. The CAN communication system cannot detect trouble in the sub bus line of the DLC3 even though the DLC3 is also connected to the CAN communication system.