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Home >> Lexus >> 2008 >> IS 250 RWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 33 (Supplemental Restraint System) >> Occupant Classification System >> DTC B1773 Belt Tension Sensor Circuit Malfunction; DTC B1776 Seat Belt Tension Sensor Power Source Circuit Malfunction >> Inspection Procedure

Inspection Procedure

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.

HINT:

  1. CHECK CONNECTORS 
    1. Turn the engine switch off
    2. Disconnect the cable from the negative (-) battery terminal
    3. Check that the connectors are properly connected to the occupant classification ECU and the seat belt tension sensor

      OK: The connectors are properly connected. 

      HINT

      If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection

    4. Disconnect the connectors from the occupant classification ECU and the seat belt tension sensor
    5. Check that the terminals of the connectors are not damaged

      OK: The terminals are not deformed or damaged. 

    NG: REPLACE WIRE HARNESS 

    OK: Go to next step 

  2. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO B+) 
    1. Connect the cable to the negative (-) battery terminal
    2. Turn the engine switch on (IG)
    3. Measure the voltage according to the value(s) in the table below

      Standard Voltage 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Switch Condition Specified Condition
      T16-8 (GBT) - Body ground Engine switch on (IG) Below 1 V
      T16-16 (BT) - Body ground Engine switch on (IG) Below 1 V
      T16-17 (VBT) - Body ground Engine switch on (IG) Below 1 V
      4. Fig 1: Identifying Seat Belt Tension Sensor Circuit (Short To B+)
      G05757112Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: Go to step  10

    OK: Go to next step 

  3. CHECK SEAT BELT TENSION SENSOR CIRCUIT (OPEN) 
    1. Turn the engine switch off
      Fig 2: Identifying Seat Belt Tension Sensor Circuit (Open)
      G05757113Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the cable from the negative (-) battery terminal.
    3. Using SST, connect terminals 1 (GBT) and 3 (BT), and connect terminals 1 (GBT) and 2 (VBT) of connector E.
      NOTE: Do not forcibly insert SST into the terminals of the connector when connecting the wire.

      SST 09843-18040 

    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-8 (GBT) - T16-16 (BT) Always Below 1 Ω
      T16-8 (GBT) - T16-17 (VBT) Always Below 1 Ω

    NG: Go to step  11

    OK: Go to next step 

  4. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO GROUND) 
    1. Disconnect SST from connector E
    2. Measure the resistance according to the value(s) in the table below

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-8 (GBT) - Body ground Always 1 MΩ or higher
      T16-16 (BT) - Body ground Always 1 MΩ or higher
      T16-17 (VBT) - Body ground Always 1 MΩ or higher
      3. Fig 3: Identifying Seat Belt Tension Sensor Circuit (Short To Ground)
      G05757114Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: Go to step  12

    OK: Go to next step 

  5. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-16 (BT) - T16-8 (GBT) Always 1 MΩ or higher
      T16-17 (VBT) - T16-8 (GBT) Always 1 MΩ or higher
      2. Fig 4: Identifying Seat Belt Tension Sensor Circuit (Short)
      G05757115Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: Go to step  13

    OK: Go to next step 

  6. CHECK DTC 
    1. Connect the connectors to the occupant classification ECU and the seat belt tension sensor
    2. Connect the cable to the negative (-) battery terminal
    3. Turn the engine switch on (IG)
    4. Clear the DTCs stored in the occupant classification ECU (See DTC CHECK / CLEAR  )
    5. Clear the DTCs stored in the center airbag sensor assembly (See DTC CHECK / CLEAR  )
    6. Turn the engine switch off
    7. Turn the engine switch on (IG)
    8. Check for DTCs (See DTC CHECK / CLEAR  )

      OK: DTC B1773 and B1776 are not output. 

      HINT

      Codes other than B1773 and B1776 may be output at this time, but they are not related to this check

    NG: Go to step 7 

    OK: USE SIMULATION METHOD TO CHECK  (See DIAGNOSIS SYSTEM  )

  7. INSPECT FRONT SEAT OUTER BELT ASSEMBLY RH 
    1. Turn the engine switch off
    2. Disconnect the cable from the negative (-) battery terminal
    3. Replace the front seat outer belt assembly RH with a known good part (See REMOVAL )

      HINT

      Perform an inspection using known good parts from another vehicle if possible

    4. Connect the cable from the negative (-) battery terminal
    5. Turn the engine switch on (IG)
    6. Clear the DTCs stored in the occupant classification ECU (See REMOVAL )
    7. Clear the DTCs stored in the center airbag sensor assembly (See DTC CHECK / CLEAR  )
    8. Turn the engine switch off
    9. Turn the engine switch on (IG)
    10. Check for DTCs (See DTC CHECK / CLEAR  )

      OK: DTC B1773 and B1776 are not output. 

      HINT

      Codes other than B1773 and B1776 may be output at this time, but they are not related to this check

    NG: Go to step 8 

    OK: END 

  8. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect the Techstream to the DLC3
    2. Turn the engine switch on (IG).
    3. Using the Techstream, save the ECU data from the ECU which has been installed on the vehicle (See REGISTRATION  )
    4. Turn the engine switch off
    5. Disconnect the cable from the negative (-) battery terminal
    6. Replace the occupant classification ECU (See REMOVAL  )
    7. Connect the cable to the negative (-) battery terminal.
    8. Turn the engine switch on (IG).
    9. Using the Techstream, load the previous ECU data stored into the new ECU (See REGISTRATION  )
    10. Turn the engine switch off.
    11. Turn the engine switch on (IG)
    12. Clear the DTCs stored in the memory (See DTC CHECK / CLEAR  )

      HINT

      If the DTCs are not cleared at this time, past DTC will remain

  9. PERFORM SENSITIVITY CHECK 
    1. Perform the sensitivity check (See INITIALIZATION  )

    NEXT: END 

  10. CHECK FRONT SEAT WIRE RH (SHORT TO B+) 
    1. Turn the engine switch off.
    2. Disconnect the cable from the negative (-) battery terminal.
    3. Disconnect the floor wire connector from the front seat wire RH
    4. Connect the cable to the negative (-) battery terminal
    5. Turn the engine switch on (IG)
    6. Measure the voltage according to the value(s) in the table below

      Standard Voltage 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Switch Condition Specified Condition
      T16-8 (GBT) - Body ground Engine switch on (IG) Below 1 V
      T16-16 (BT) - Body ground Engine switch on (IG) Below 1 V
      T16-17 (VBT) - Body ground Engine switch on (IG) Below 1 V
      7. Fig 5: Identifying Front Seat Wire RH (Short To B+)
      G05757116Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE FRONT SEAT WIRE RH 

    OK: REPLACE FLOOR WIRE 

  11. CHECK FRONT SEAT WIRE RH (OPEN) 
    1. Disconnect the floor wire connector from the front seat wire RH
      Fig 6: Identifying Front Seat Wire RH (Open)
      G05757117Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Using SST, connect terminals 5 (BT) and 7 (GBT), and connect terminals 6 (VBT) and 7 (GBT) of connector C
      NOTE: Do not forcibly insert SST into the terminals of the connector when connecting the wire.

      SST 09843-18040 

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-16 (BT) - T16-8 (GBT) Always Below 1 Ω
      T16-17 (VBT) - T16-8 (GBT) Always Below 1 Ω

    NG: REPLACE FRONT SEAT WIRE RH 

    OK: REPLACE FLOOR WIRE 

  12. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND) 
    1. Disconnect the floor wire connector from the front seat wire RH.
    2. Measure the resistance according to the value(s) in the table below

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-8 (GBT) - Body ground Always 1 MΩ or higher
      T16-16 (BT) - Body ground Always 1 MΩ or higher
      T16-17 (VBT) - Body ground Always 1 MΩ or higher
      3. Fig 7: Identifying Front Seat Wire RH (Short To Ground)
      G05757118Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE FRONT SEAT WIRE RH 

    OK: REPLACE FLOOR WIRE 

  13. CHECK FRONT SEAT WIRE RH (SHORT) 
    1. Disconnect the floor wire connector from the front seat wire RH.
    2. Measure the resistance according to the value(s) in the table below

      Standard Resistance 

      TESTER CONNECTION SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      T16-16 (BT) - T16-8 (GBT) Always 1 MΩ or higher
      T16-17 (VBT) - T16-8 (GBT) Always 1 MΩ or higher
      3. Fig 8: Identifying Front Seat Wire RH (Short)
      G05757119Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE FRONT SEAT WIRE RH 

    OK: REPLACE FLOOR WIRE 

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