LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2011 >> IS F >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Multiplex Communication System (Diagnostics - Introduction)) >> Multiplex Communication System >> System Description >> System Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

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.
  1. MULTIPLEX COMMUNICATION SYSTEM BASICS 
    1. The AVALON multiplex communication uses serial communication, which converts multiple pieces of information into serial communication data. As a result, they can be transmitted through a single communication wire.
      Fig 1: Identifying Multiplex Serial Communication Circuit Diagram
      GTY195508Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Serial communication data consist of bits and frames. A bit is a basic unit that represents one piece of information. A bit is represented by the binary values "0" or "1". A frame is a body of data that is transmitted as a packet. A frame contains a "header" that indicates the beginning of the data and an "end" message that indicates the end of the data.
      Fig 2: Identifying Serial Communication Data Diagram
      GTY170139Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Based on serial communication, various ECUs are connected on a network to exchange various pieces of information. Such a system is called a multiplex communication system.
      1. The CAN uses a multi star style bus connection. The 3 junction connectors are connected by a main bus line. Junction connectors communicate with ECUs using a sub bus line.
        Fig 3: Identifying Junction Connectors Communication System Diagram
        GTY195507Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. The BEAN uses ring and bus styles of networks to connect ECUs. This style of connection is called a daisy chain. In a daisy chain, communication can be maintained even if there is an area that has an open circuit.
        Fig 4: Identifying Daisy Chain Communication System Diagram
        GTY189989Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      3. The AVC-LAN uses a star configuration, which is centered on the multi display or audio head unit.
        Fig 5: Identifying Multi Display Communication System Diagram
        GTY181289Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    4. Differences between CAN, BEAN and AVC-LAN
      1. Protocols, which are rules for establishing data communication, differ between the CAN, BEAN and the AVC-LAN. If ECUs use different types of data such as communication speed, communication wire, and signals, they will be unable to communicate with each other. Therefore, protocols (rules) must be established among them.
        Control Driving Control System Body Electrical Control System Body Electrical Control System
        Protocol CAN
        (ISO Standard)        		 BEAN
        (TOYOTA Original)        		 AVC-LAN
        (TOYOTA Original)
        Communication Speed 500 k bps*
        (Max. 1 M bps)        		 Max. 10 k bps* Max. 17. 8 k bps*
        Communication Wire Twisted-pair Wire AV Single Wire Twisted-pair Wire
        Drive Type Differential Voltage Drive Single Wire Voltage Drive Differential Voltage Drive
        Data Length 1 to 8 Byte (Variable) 1 to 11 Byte (Variable) 0 to 32 Byte (Variable)

        HINT: 

        *: The abbreviation "bps" stands for "bits per second" (the number of bits that can be transmitted per second).

      2. A single, Automobile Vinyl (AV) wire is used for BEAN communication. A twisted-pair wire is used for CAN and AVC-LAN communication.
        Communication Wire Outline
        AV Single Wire Lightweight single communication wire that consists of single core line surrounded by insulation. Voltage is applied to this line in order to drive communication. This system is called a "Single Wire Voltage Drive".
        • Twisted-pair Wire for AVC-LAN
        • Twisted-pair Wire for CAN
        		 Pair of lines Twisted together and covered with insulation. Communication is driven by applying positive (+) and negative (-) voltage to the 2 lines in order to send a single signal. This system, which is called "Differential Voltage Drive", can reduce noise.
        Fig 6: Identifying Multiplex Communication System Wiring Diagram
        GTY169492Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. NETWORK GATEWAY ECU 
    1. The network gateway ECU of the AVALON has the following functions:
      Function Outline
      Gateway Data for respective protocols (CAN, BEAN and AVC-LAN) are arranged differently. Therefore, it is not possible to exchange data between different protocols. For this reason, data arrangement must be converted before transferring data to a communication bus (CAN, BEAN and AVC-LAN). This conversion is called a gateway function. It is preformed by a gateway ECU.
      Diagnosis
      (only for BEAN)      		 By connecting an Techstream to DLC3 and operating the tester, technicians can access ECUs via the gateway ECU and BEAN communication bus. In this manner, DTCs for BEAN can be output, DATA LIST (for checking ECU data) can be displayed, and ACTIVE TEST (to actuate desired actuator) can be performed.
      Customize
      (only for BEAN)      		 Customized body electronics system enables control function settings of ECUs to be changed through use of an Techstream. However, this system can change settings only of ECUs that belong to the bus in which communication is centered on gateway ECU.
scientia non olet · About LEMON Manuals