DTC B1781: Front Occupant Classification Sensor RH Circuit Malfunction [08/2019 - ]: Procedure

1. Turn the engine switch on (IG), and wait for at least 60 seconds.
2. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   HINT: 

   • First clear DTCs stored in the occupant classification ECU and then 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 engine switch off.
4. Turn the engine switch on (IG), and wait for at least 60 seconds.
5. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   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.

Result: 

OK 

USE SIMULATION METHOD TO CHECK 

(Refer to DIAGNOSIS SYSTEM [08/2019 - ] )

Result: 

NG 

See step  2

1. Turn the engine 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 the front occupant detection sensor RH.

   OK

   Connectors are properly connected.

Result: 

NG 

CONNECT CONNECTORS PROPERLY 

Result: 

OK 

See step  3

1. Check that the connectors (on the occupant classification ECU side and front occupant detection sensor RH side) are not damaged (Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [08/2019 - ] ).

   OK

   Connectors are not deformed or damaged.

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  4

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the connectors from the occupant classification ECU and the front occupant detection sensor RH.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   W1-2 (SGD2) - Body ground	Engine switch on (IG)	Below 1 V
   W1-8 (SIG2) - Body ground
   W1-12 (SVC2) - Body ground

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

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W1-8 (SIG2) - W1-2 (SGD2)	Always	Below 1 Ω
   W1-12 (SVC2) - W1-2 (SGD2)

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

    Standard Resistance

    Tester Connection	Condition	Specified Condition
    W1-8 (SIG2) - W1-2 (SGD2)	Always	1 MΩ or higher
    W1-12 (SVC2) - W1-2 (SGD2)
    W1-8 (SIG2) - W1-12 (SVC2)
    W1-2 (SGD2) - Body ground
    W1-8 (SIG2) - Body ground
    W1-12 (SVC2) - Body ground

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  5

1. Connect the connectors to the occupant classification ECU and the front occupant detection sensor RH.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   HINT: 

   • First clear DTCs stored in the occupant classification ECU and then 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 engine switch off.
6. Turn the engine switch on (IG), and wait for at least 60 seconds.
7. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   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.

Result: 

OK 

USE SIMULATION METHOD TO CHECK 

(Refer to DIAGNOSIS SYSTEM [08/2019 - ] )

Result: 

NG 

See step  6

1. Turn the engine 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 [08/2019 - ] )

   HINT: 

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

Result: 

NEXT 

See step  7

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Using the Techstream, perform the zero point calibration (Refer to INITIALIZATION [08/2019 - ] ).

Result: 

NEXT 

See step  8

1. Using the Techstream, perform the sensitivity check (Refer to INITIALIZATION [08/2019 - ] ).

   Standard range

   27 to 33 kg (59.5 to 72.8 lb)

Result: 

NG 

See step  10

Result: 

OK 

See step  9

1. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   HINT: 

   • First clear DTCs stored in the occupant classification ECU and then 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 engine switch off.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

   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.

Result: 

OK 

END 

Result: 

NG 

See step  10

1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the front seat with adjuster frame assembly RH.
   • for Manual seat (Refer to DISASSEMBLY [08/2017 - ] )
   • for Power seat (Refer to DISASSEMBLY [08/2017 - ] )

   HINT: 

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

Result: 

NEXT 

See step  11

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Using the Techstream, perform the zero point calibration (Refer to INITIALIZATION [08/2019 - ] ).

Result: 

NEXT 

See step  12

1. Using the Techstream, perform the sensitivity check (Refer to INITIALIZATION [08/2019 - ] ).

   Standard range

   27 to 33 kg (59.5 to 72.8 lb)

Result: 

NEXT 

END