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Home >> Lexus >> 2017 >> CT 200h Base >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System - Diagnostic Codes & Symptom Tests >> Occupant Classification System >> DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction [08/2014 - ] >> Procedure

DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction [08/2014 - ]: Procedure

  1. CHECK CONNECTORS 
    1. Turn the power switch off.
    2. Disconnect the cable from the negative (-) auxiliary battery terminal.
    3. Check that the connectors are properly connected to the 4 occupant classification sensors and occupant detection ECU.

      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 4 occupant classification sensors and occupant detection ECU.
    5. Check that the terminals of the connectors are not damaged.

      OK

      The terminals are not deformed or damaged.

    Result:  NG

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result:  OK

    OK 

    Refer to  2

  2. CHECK FRONT SEAT WIRE RH (SHORT TO B+) 
    1. Connect the cable to the negative (-) auxiliary battery terminal.
      GTY536111Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the power switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      W3-5 (SVC3) - Body ground Power switch on (IG) Below 1 V
      W3-6 (SVC4) - Body ground Power switch on (IG) Below 1 V
      W3-11 (SVC1) - Body ground Power switch on (IG) Below 1 V
      W3-12 (SVC2) - Body ground Power switch on (IG) Below 1 V
      TEXT IN ILLUSTRATION

      *1 4 Occupant Classification Sensors
      *2 Occupant Detection ECU
      *3 Front Seat Wire RH
      *4 Connector B
      *a Front view of wire harness connector
      (to Occupant Detection ECU)

    Result:  NG

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result:  OK

    OK 

    Refer to  3

  3. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND) 
    1. Turn the power switch off.
      GTY536111Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the cable from the negative (-) auxiliary battery terminal.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      W3-5 (SVC3) - Body ground Always 1 MΩ or higher
      W3-6 (SVC4) - Body ground Always 1 MΩ or higher
      W3-11 (SVC1) - Body ground Always 1 MΩ or higher
      W3-12 (SVC2) - Body ground Always 1 MΩ or higher
      TEXT IN ILLUSTRATION

      *1 4 Occupant Classification Sensors
      *2 Occupant Detection ECU
      *3 Front Seat Wire RH
      *4 Connector B
      *a Front view of wire harness connector
      (to Occupant Detection ECU)

    Result:  NG

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result:  OK

    OK 

    Refer to  4

  4. CHECK FRONT SEAT WIRE RH (OPEN) 
    1. Measure the resistance according to the value(s) in the table below.
      GTY522878Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      W3-5 (SVC3) - W7-1 (SVC3) Always Below 1 Ω
      W3-6 (SVC4) - W1-1 (SVC4) Always Below 1 Ω
      W3-11 (SVC1) - W6-1 (SVC1) Always Below 1 Ω
      W3-12 (SVC2) - W2-1 (SVC2) Always Below 1 Ω
      TEXT IN ILLUSTRATION

      *1 4 Occupant Classification Sensors *2 Occupant Detection ECU
      *3 Front Seat Wire RH *4 Connector B
      *5 Connector C *6 Front Occupant Classification Sensor LH
      *7 Rear Occupant Classification Sensor RH *8 Front Occupant Classification Sensor RH
      *9 Rear Occupant Classification Sensor LH - -
      *a Front view of wire harness connector
      (to Occupant Detection ECU)      		 *b Front view of wire harness connector
      (to 4 Occupant Classification Sensors)

    Result:  NG

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result:  OK

    OK 

    Refer to  5

  5. CHECK FRONT SEAT WIRE RH (SHORT) 
    1. Measure the resistance according to the value(s) in the table below.
      GTY536111Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      W3-5 (SVC3) - W3-6 (SVC4) Always 1 MΩ or higher
      W3-5 (SVC3) - W3-11 (SVC1) Always 1 MΩ or higher
      W3-5 (SVC3) - W3-12 (SVC2) Always 1 MΩ or higher
      W3-6 (SVC4) - W3-11 (SVC1) Always 1 MΩ or higher
      W3-6 (SVC4) - W3-12 (SVC2) Always 1 MΩ or higher
      W3-11 (SVC1) - W3-12 (SVC2) Always 1 MΩ or higher
      TEXT IN ILLUSTRATION

      *1 4 Occupant Classification Sensors
      *2 Occupant Detection ECU
      *3 Front Seat Wire RH
      *4 Connector B
      *a Front view of wire harness connector
      (to Occupant Detection ECU)

    Result:  NG

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result:  OK

    OK 

    Refer to  6

  6. CHECK DTC 
    1. Connect the connectors to the occupant detection ECU and 4 occupant classification sensors.
    2. Connect the cable to the negative (-) auxiliary battery terminal.
    3. Turn the power switch on (IG).
    4. Clear the DTCs stored in the occupant detection ECU (Refer to DTC Check / Clear [08/2014 - ] ).
    5. Clear the DTCs stored in the airbag sensor assembly (Refer to DTC Check / Clear [08/2014 - ] ).
    6. Turn the power switch off.
    7. Turn the power switch on (IG).
    8. Check for DTCs (Refer to DTC Check / Clear [08/2014 - ] ).

      OK

      DTC B1793 is not output.

      HINT: 

      Codes other than DTC B1793 may be output at this time, but they are not related to this check.

    Result:  OK

    OK 

    USE SIMULATION METHOD TO CHECK 

    (Refer to How To Proceed With Troubleshooting [08/2014 - ] )

    Result:  NG

    NG 

    Refer to  7

  7. REPLACE FRONT SEAT CUSHION SPRING ASSEMBLY 
    1. Turn the power switch off.
    2. Disconnect the cable from the negative (-) auxiliary battery terminal.
    3. Replace the front seat cushion spring assembly (Refer to Disassembly [08/2014 - ] for Manual seat. Refer to Disassembly [08/2014 - ] for Power seat).

    Result:  NEXT

    NEXT 

    Refer to  8

  8. PERFORM ZERO POINT CALIBRATION 
    1. Connect the cable to the negative (-) auxiliary battery terminal.
    2. Turn the power switch on (IG).
    3. Using the Techstream, perform Zero Point Calibration (Refer to Initialization [08/2014 - ] ).

    Result:  NEXT

    NEXT 

    Refer to  9

  9. PERFORM SENSITIVITY CHECK 
    1. Using the Techstream, perform Sensitivity Check (Refer to Initialization [08/2014 - ] ).

    Result:  NEXT

    NEXT 

    END 

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