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Home >> Lexus >> 2006 >> RX 400h FWD >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Supplemental Restraint System >> Airbag System >> Diagnosis System

Diagnosis System

  1. CHECK DLC3 
    1. The multiplex network body ECU uses ISO 9141-2 BEAN for its communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.
      Fig 1: Identifying Connector Terminals DLC3
      G04114169Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TERMINALS DESCRIPTION

      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 11 to 14 V
      CANH (6) - CANL (14) HIGH-level CAN bus line Ignition switch off 54 to 67 Ω
      CANH (6) - Battery positive HIGH-level CAN bus line Ignition switch off 1 MΩ or higher
      CANH (6) - CG (4) HIGH-level CAN bus line Ignition switch off 3 MΩ or higher
      CANL (14) - Battery positive LOW-level CAN bus line Ignition switch off 1 MΩ or higher
      CANL (14) - CG (4) LOW-level CAN bus line Ignition switch off 3 MΩ or higher

      HINT:

      If the display shows a communication error message when connecting the cable of the intelligent tester to the DLC3, turning the ignition switch to the ON position and operating the intelligent tester, there is a problem on the vehicle side or tool side.

      • If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.
      • If communication is still not possible 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.
  2. SYMPTOM SIMULATION 

    HINT:

    The most difficult case in troubleshooting is when no symptoms occur. In such cases, a thorough customer problem analysis must be carried out. Then the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be simulated. No matter how experienced or skilled a technician may be, if he proceeds to troubleshoot without confirming the problem symptoms, he will likely overlook something important and make a wrong guess at some points in the repair operation.

    This leads to a standstill in troubleshooting.

    1. Vibration method: When vibration seems to be the major cause.

      HINT:

      Perform the simulation method only during the primary check period (for approximately 6 seconds after the ignition switch is turned to the ON position).

      1. Slightly vibrate the part of the sensor considered to be the problem with your fingers and check whether the malfunction occurs.
        Fig 2: Shaking Wire Harness Vertically And Horizontally
        G04114170Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

        HINT:

        Shaking the relays too strongly may result in open relays.

      2. Slightly shake the connector vertically and horizontally.
      3. Slightly shake the wire harness vertically and horizontally.

        The connector joint and fulcrum of the vibration are the major areas to be checked thoroughly.

  3. FUNCTION OF SRS WARNING LIGHT 
    1. Primary check.
      1. Turn the ignition switch to the LOCK position. After 2 seconds or more, turn the ignition switch to the ON position. The SRS warning light comes on for approximately 6 seconds and the diagnosis of the SRS airbag system (including the seat belt pretensioner and front passenger occupant classification system) is performed.

        HINT:

        If trouble is detected during the primary check, the SRS warning light remains on even after the primary check period (for approximately 6 seconds) has elapsed.

    2. Constant check.
      1. After the primary check, the center airbag sensor assembly constantly monitors the airbag system for trouble.

        HINT:

        If trouble is detected during the constant check, the center airbag sensor assembly functions as follows:

        • The SRS warning light comes on.
        • The SRS warning light goes off, and then comes on. This blinking pattern indicates a source voltage drop. The SRS warning light goes off 10 seconds after the source voltage returns to normal.
    3. Review.
      1. When the airbag system is normal:

        The SRS warning light comes on only for the primary check period (for approximately 6 seconds after the ignition switch is turned to the ON position).

      2. When the airbag system has trouble:
        • The SRS warning light remains on even after the primary check period has elapsed.
        • The SRS warning light goes off after the primary check, but comes on again during the constant check.
        • The SRS warning light does not come on when turning the Ignition switch from the LOCK to the ON position.

        HINT:

        The center airbag sensor assembly keeps the SRS warning light on if the airbag has been deployed.

  4. SRS WARNING LIGHT CHECK 
    1. Turn the ignition switch to the ON position, and check that the SRS warning light comes on for approximately 6 seconds (primary check).
    2. Check that the SRS warning light goes off approximately 6 seconds after the ignition switch is turned to the ON position (constant check).
      Fig 3: Identifying SRS Warning Light Check
      G04114171Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT:

      When any of the following symptoms occur, refer to the PROBLEM SYMPTOMS TABLE  .

      • The SRS warning light comes on occasionally, after the primary check period has elapsed.
      • The SRS warning light comes on, but a DTC is not output.
      • When the ignition switch is turned to ON position, the SRS warning light does not come on.
  5. FUNCTION OF PASSENGER AIRBAG ON/OFF INDICATOR 
    1. Initial check
      1. Turn the ignition switch to the ON position.
      2. The passenger airbag ON/OFF indicator comes on for approximately 4 seconds, then goes off for approximately 2 seconds.
      3. Approximately 6 seconds after the ignition switch is turned to the ON position, the passenger airbag ON/OFF indicator will be ON/ OFF depending on the conditions listed below.
        INDICATOR CONDITION

        Condition "ON" indicator "OFF" indicator
        Vacant OFF OFF
        Adult is seated. ON OFF
        Child is seated. OFF ON
        Child restraint system is set. OFF ON
        Front passenger occupant classification failure OFF ON

        HINT:

        • The passenger airbag ON/OFF indicator is based on the timing chart below in order to check the indicator light circuit.
          Fig 4: Identifying Blinking Pattern
          G04114172Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
        • When the front passenger occupant classification system has trouble, both the SRS warning light and the passenger airbag ON/OFF indicator come on. In this case, check the DTCs in the "AIRBAG SYSTEM" first. Then troubleshoot the occupant classification system if DTC B1150/23 is detected and troubleshoot the passenger airbag ON/OFF indicator if DTC B1152/28 is detected.
  6. CHECK PASSENGER AIRBAG ON/OFF INDICATOR CHECK 
    1. Turn the ignition switch to the ON position.
    2. Check that the passenger airbag ON/OFF indicator ("ON" and "OFF") comes on for approximately 4 seconds, then goes off for approximately 2 seconds.
      Fig 5: Identifying Passenger Airbag On/Off Indicator
      G04114173Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT:

      Refer to the table in the previous step regarding the passenger airbag ON/ OFF indicator when the ignition switch is turned to the ON position and approximately 6 seconds pass.

  7. ACTIVATION PREVENTION MECHANISM 
    1. FUNCTION OF ACTIVATION PREVENTION MECHANISM
      1. An activation prevention mechanism is built into the connector (on the center airbag sensor assembly side) of the airbag system squib circuit to prevent accidental airbag activation.
      2. This mechanism closes the circuit when the connector is disconnected by bringing the short spring into contact with the terminals and shutting off external electricity to prevent accidental airbag activation.
    2. RELEASE METHOD OF ACTIVATION PREVENTION MECHANISM
      1. To release the activation prevention mechanism, insert a piece of paper with the same thickness as the male terminal (approximately 0.5 mm (0.020 in.)) between the terminals and the short spring to break the connection.
      2. Refer to the illustrations on the next 2 pages for connectors used in the activation prevention mechanism and its release method.
        CAUTION: Never release the activation prevention mechanism on the squib connector even when inspecting with the squib disconnected.
        NOTE:
        • Do not release the activation prevention mechanism unless specially directed by the troubleshooting procedure.
        • To prevent the terminal and the short spring from becoming damaged, always use a piece of paper with the same thickness as the male terminal.
        Fig 6: Communication Diagram Sensor Supplemental Restraint System
        G04114174Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
        Fig 7: Locating Short Spring Center Airbag Sensor Assembly
        G04114175Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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