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Diagnosis System

  1. DESCRIPTION 
    1. The transponder key ECU controls the vehicle's immobilizer system functions, immobilizer system data and Diagnostic Trouble Code (DTC) can be read through the vehicle's Data Link Connector 3 (DLC3). In some cases, a malfunction may be occurring in the immobilizer system even though the security indicator light is not illuminated. When the system seems to be malfunctioning, use the Techstream to check for malfunctions and perform repairs.
  2. CHECK DLC3 
    1. The vehicle's ECU uses ISO 15765-4 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.
      Fig 1: Identifying DLC3 Connector Terminals
      G04828034Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      RESISTANCE SPECIFICATION

      Symbols (Terminal No.) Terminal Description Condition Specified Condition
      SIL (7) - SG (5) Bus "+" line During transmission Pulse generation
      CG (4) - Body ground Chassis ground Always Below 1 Ω
      SG (5) - Body ground Signal ground Always Below 1 Ω
      BAT (16) - Body ground Battery positive Always 10 to 14 V
      CANH (6) - CANL (14) CAN bus line Ignition switch OFF(1) 54 to 69 Ω
      CANH (6) - CG (4) HIGH-level CAN bus line Ignition switch OFF(1) 200 Ω or higher
      CANL (14) - CG (4) LOW-level CAN bus line Ignition switch OFF(1) 200 Ω or higher
      CANH (6) - BAT (16) HIGH-level CAN bus line Ignition switch OFF(1) 6 kΩ or higher
      CANL (14) - BAT (16) LOW-level CAN bus line Ignition switch OFF(1) 6 kΩ or higher
      (1) Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the ignition switch, any other switches or the doors.

      If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.

    2. Connect the cable of the Techstream to the DLC3, turn the ignition switch to the ON position and attempt to use the Techstream. If the screen displays a communication error message, a problem exists in the vehicle side of the tester side.

      HINT:

      • If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.
      • If communication is still impossible when the tool is connected to another vehicle, the problem is probably in the tool itself. Consult the Service Department listed in the tool's instruction manual.
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