DTC B1793 Occupant Classification Sensor Power Supply Circuit Malfunction: Wiring Diagram

Fig 1: Occupant Classification Sensor Power Supply Circuit Wiring Diagram

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

• If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of the seat cushion.
• In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat only as necessary.

1. CHECK DTC 
   1. Turn the ignition switch to the ON position.
   2. Clear the DTCs stored in memory (See DTC CHECK / CLEAR  ).

      HINT:

      First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

   3. Turn the ignition switch to the LOCK position.
   4. Turn the ignition switch to the ON position.
   5. Check the DTCs (See DTC CHECK / CLEAR  ).

      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.

   OK : USE SIMULATION METHOD TO CHECK 

   NG : GO TO NEXT STEP 

2. CHECK CONNECTION OF CONNECTORS 
   1. Turn the ignition switch to the LOCK position.
   2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
   3. Check that the connectors are properly connected to the occupant classification ECU and the occupant classification sensors.

      OK: The connectors are connected. 

   NG : CONNECT CONNECTORS, THEN GO TO STEP   1 

   OK : GO TO NEXT STEP 

3. CHECK FRONT SEAT WIRE RH (SHORT TO B+) 
   1. Disconnect the connectors from the occupant classification ECU and the 4 occupant classification sensors.
   2. Connect the negative (-) terminal cable to the battery.
   3. Turn the ignition switch to the ON position.
   4. Measure the voltage according to the value(s) in the table below.

      Voltage 

      VOLTAGE SPECIFIED CONDITIONS
      
      

      Tester connection	Condition	Specified condition
      O4-5 (SVC3) - Body ground	Ignition switch ON	Below 1 V
      O4-6 (SVC4) - Body ground	Ignition switch ON	Below 1 V
      O4-11 (SVC1) - Body ground	Ignition switch ON	Below 1 V
      O4-12 (SVC2) - Body ground	Ignition switch ON	Below 1 V

   NG : REPAIR OR REPLACE FRONT SEAT WIRE RH 

   Fig 2: Identifying Front Seat Wire RH (Short To B+)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK : GO TO NEXT STEP 

4. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND) 
   1. Turn the ignition switch to the LOCK position.
   2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
   3. Measure the resistance according to the value(s) in the table below.

      Resistance 

      RESISTANCE SPECIFIED CONDITIONS
      
      

      Tester connection	Condition	Specified condition
      O4-5 (SVC3) - Body ground	Always	1 MΩ or higher
      O4-6 (SVC4) - Body ground	Always	1 MΩ or higher
      O4-11 (SVC1) - Body ground	Always	1 MΩ or higher
      O4-12 (SVC2) - Body ground	Always	1 MΩ or higher

      Fig 3: Identifying Front Seat Wire RH (Short To Ground)

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   NG : REPAIR OR REPLACE FRONT SEAT WIRE RH 

   OK : GO TO NEXT STEP 

5. CHECK FRONT SEAT WIRE RH (OPEN) 
   1. Measure the resistance according to the value(s) in the table below.

      Resistance 

      RESISTANCE SPECIFIED CONDITIONS
      
      

      Tester connection	Condition	Specified condition
      O4-5 (SVC3) - O7-1 (SVC3)	Always	Below 1 Ω
      O4-6 (SVC4) - O8- 1 (SVC4)	Always	Below 1 Ω
      O4-11 (SVC1) - O5-1 (SVC1)	Always	Below 1 Ω
      O4-12 (SVC2) - O6-1 (SVC2)	Always	Below 1 Ω

   NG : REPAIR OR REPLACE FRONT SEAT WIRE RH 

   Fig 4: Identifying Front Seat Wire RH (Open)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK : GO TO NEXT STEP 

6. CHECK FRONT SEAT WIRE RH (SHORT) 
   1. Measure the resistance according to the value(s) in the table below.

      Resistance 

      RESISTANCE SPECIFIED CONDITIONS
      
      

      Tester connection	Condition	Specified condition
      O4-5 (SVC3) - O4-6 (SVC4)	Always	1 MΩ or higher
      O4-6 (SVC4) - O4-11 (SVC1)	Always	1 MΩ or higher
      O4-11 (SVC1) - O4-12 (SVC2)	Always	1 MΩ or higher
      O4-12 (SVC2) - O4-5 (SVC3)	Always	1 MΩ or higher
      O4-12 (SVC2) - O4-6 (SVC4)	Always	1 MΩ or higher
      O4-11 (SVC1) - O4-5 (SVC3)	Always	1 MΩ or higher

   NG : REPAIR OR REPLACE FRONT SEAT WIRE RH 

   Fig 5: Identifying Front Seat Wire RH (Short)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK : GO TO NEXT STEP 

7. CHECK DTC 
   1. Connect the connectors to the occupant classification ECU and the 4 occupant classification sensors.
   2. Connect the negative (-) terminal cable to the battery.
   3. Turn the ignition switch to the ON position.
   4. Clear the DTCs stored in memory (See DTC CHECK / CLEAR  ).

      HINT:

      First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

   5. Turn the ignition switch to the LOCK position.
   6. Turn the ignition switch to the ON position.
   7. Check the DTCs (See DTC CHECK / CLEAR  ).

      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.

   OK : USE SIMULATION METHOD TO CHECK 

   NG : GO TO NEXT STEP 

8. REPLACE OCCUPANT CLASSIFICATION ECU 
   1. Turn the ignition switch to the LOCK position.
   2. Disconnect the negative (-) terminal cable from the battery.
   3. Replace the OCCUPANT CLASSIFICATION ECU  .

      HINT:

      Perform the inspection using parts from a normal vehicle if possible.

9. PERFORM ZERO POINT CALIBRATION 
   1. Connect the negative (-) terminal cable to the battery.
   2. Connect the intelligent tester to the DLC3.
   3. Turn the ignition switch to the ON position.
   4. Using the intelligent tester, perform "Zero point calibration" (See  1 ).

      OK: The "COMPLETED" is displayed. 

   NG : Go to step   12 

   OK : GO TO NEXT STEP 

10. PERFORM SENSITIVITY CHECK 
    1. Using the intelligent tester, perform "Sensitivity check" (See  1 ).

       Standard values: 27 to 33 kg (59.52 to 72.75 lb) 

    NG : Go to step   12 

    OK : GO TO NEXT STEP 

11. CHECK DTC 
    1. Connect the negative (-) terminal cable to the battery.
    2. Turn the ignition switch to the ON position.
    3. Clear the DTCs stored in memory (See DTC CHECK / CLEAR  ).

       HINT:

       First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

    4. Turn the ignition switch to the LOCK position.
    5. Turn the ignition switch to the ON position.
    6. Check the DTCs (See DTC CHECK / CLEAR  ).

       OK: DTC B1793 is not output. 

       HINT:

       Codes other than DTC B1793 may be output at this time, but they are related to this check.

    OK : END 

    NG : GO TO NEXT STEP 

12. REPLACE FRONT SEAT ASSEMBLY RH 
    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery.
    3. Replace the front seat assembly RH (See REMOVAL ).
13. PERFORM ZERO POINT CALIBRATION 
    1. Connect the negative (-) terminal cable to the battery.
    2. Connect the intelligent tester to the DLC3.
    3. Turn the ignition switch to the ON position.
    4. Using the intelligent tester, perform "Zero point calibration" (See  1 ).

       OK: The "COMPLETED" is displayed. 

14. PERFORM SENSITIVITY CHECK 
    1. Using the intelligent tester, perform "Sensitivity check" (See  1 ).

       Standard values: 27 to 33 kg (59.52 to 72.75 lb) 

    END