DTC B1781: Front Occupant Classification Sensor RH Circuit Malfunction: Procedure

1. Turn the ignition switch to ON, and wait for at least 60 seconds.
2. Clear the DTCs. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
3. Turn the ignition switch off.
4. Turn the ignition switch to ON, and wait for at least 60 seconds.
5. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1781 is not output.

   HINT: 

   DTCs other than DTC B1781 may be output at this time, but they are not related to this check.

NG → See step   2 

OK → See step   13 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Check that the connectors are properly connected to the occupant classification ECU and front occupant classification sensor RH.

   OK

   Connectors are properly connected.

NG → CONNECT CONNECTOR 

OK: Go to next step 

1. Disconnect the connectors from the occupant classification ECU and front occupant classification sensor RH.
2. Check that the connectors (on the occupant classification ECU side and front occupant classification sensor RH side) are not damaged. Refer to DIAGNOSIS SYSTEM .

   OK

   Connectors are not deformed or damaged.

NG → See step   14 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
   Fig 1: Checking Front Seat Wire RH (Front Occupant Classification Sensor RH - Occupant Classification ECU)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   z6-2 (SGD2) - Body ground	Ignition switch ON	Below 1 V
   z6-8 (SIG2) - Body ground
   z6-12 (SVC2) - Body ground

3. Turn the ignition switch off.
4. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
5. Using service wires, connect terminals 1 (SVC2) and 3 (SGD2), and terminals 2 (SIG2) and 3 (SGD2) of connector C.
   NOTE:

   Do not forcibly insert the service wires into the terminals of the connector.

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   z6-8 (SIG2) - z6-2 (SGD2)	Always	Below 1 Ω
   z6-12 (SVC2) - z6-2 (SGD2)

7. Disconnect the service wires from connector C.
8. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   z6-8 (SIG2) - z6-2 (SGD2)	Always	1 MΩ or higher
   z6-12 (SVC2) - z6-2 (SGD2)
   z6-8 (SIG2) - z6-12 (SVC2)
   z6-2 (SGD2) - Body ground
   z6-8 (SIG2) - Body ground
   z6-12 (SVC2) - Body ground

   TEXT IN ILLUSTRATION
   
   

   *1	Front Seat Wire RH
   *2	Front Occupant Classification Sensor RH
   *3	Occupant Classification ECU
   *4	Service Wire
   *5	Connector C
   *6	Connector B
   *a	Front view of wire harness connector (to Front Occupant Classification Sensor RH)
   *b	Front view of wire harness connector (to Occupant Classification ECU)

NG → See step   14 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and front occupant classification sensor RH.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the ignition switch to ON, and wait for at least 60 seconds.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
5. Turn the ignition switch off.
6. Turn the ignition switch to ON, and wait for at least 60 seconds.
7. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1781 is not output.

   HINT: 

   DTCs other than DTC B1781 may be output at this time, but they are not related to this check.

NG → See step   6 

OK → See step   13 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the occupant classification ECU. Refer to REMOVAL .

   HINT: 

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

NEXT: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Turn the ignition switch to ON.
3. Perform the zero point calibration. Refer to INITIALIZATION .

   OK

   "Zero Point Calibration is complete." is displayed.

NG → See step   10 

OK: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

   Standard

   27 to 33 kg (59.5 to 72.8 lb)

NG → See step   10 

OK: Go to next step 

1. Clear the DTCs. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
2. Turn the ignition switch off.
3. Turn the ignition switch to ON, and wait for at least 60 seconds.
4. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1781 is not output.

   HINT: 

   DTCs other than DTC B1781 may be output at this time, but they are not related to this check.

NG → See step   10 

OK → END (OCCUPANT CLASSIFICATION ECU IS DEFECTIVE) 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the separate type front seat cushion spring RH. Refer to DISASSEMBLY .

   HINT: 

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

NEXT: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Turn the ignition switch to ON.
3. Perform the zero point calibration. Refer to INITIALIZATION .

   OK

   "Zero Point Calibration is complete." is displayed.

NEXT: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

   Standard

   27 to 33 kg (59.5 to 72.8 lb)

NEXT → END (SEPARATE TYPE FRONT SEAT CUSHION SPRING RH IS DEFECTIVE)