System Description [10/2023 - ]

WARNING: This page is about a different car, the 2024 Lexus LS 500h. However, it is still accessible from the selected car via links, so may be relevant.

BRIEF DESCRIPTION

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.

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.)
Many ECUs or sensors installed to the vehicle operate by sharing information and communicating with each other.
2 resistors which are necessary for communication are used in a CAN bus main line.

DEFINITION OF TERMS

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Central bus
  1. The central bus is a term used to describe all buses directly connected to the central gateway ECU (network gateway ECU).
    HINT:
    
    A bus is displayed as Bus on the "Communication Bus Check" screen of the GTS.
2. Sub bus
  1. A sub bus is a bus that has a gateway function equipped ECU in order to communicate with the central bus and other sub buses.
    HINT:
    - A sub bus is displayed as Sub bus on the "Communication Bus Check" screen of the GTS.
    - When Sub bus is selected on the "Communication Bus Check" screen, ECUs and sensors connected to non-CAN networks such as LIN may also be displayed in addition to the ECUs and sensors connected to sub buses in the CAN network.
3. Local bus
  1. A local bus is a bus that does not have the ability to communicate with other buses. ECUs and sensors on a local bus can only communicate with other ECUs and sensors on the same bus.
    NOTE:
    Gateway function not equipped ECU is a generic name for ECUs not connected to the central gateway ECU (network gateway ECU) with a gateway function.
4. CAN J/C
  1. A CAN junction connector is a connector that connects branch lines to a main bus.
5. Main bus
  1. A main bus line is the wire harness that runs between the 2 terminating resistors of a bus.
6. Branch
  1. A branch line is a wire harness that connects an ECU or sensor to a main bus line.
7. Terminating resistors
  1. Terminating resistors which maintain a stable signal inside the CAN bus are installed. 2 resistors of 120 Ω each located at each end of the bus are necessary.