DTC B1780: Front Occupant Classification Sensor LH Circuit Malfunction [12/2019 - 11/2023]: Procedure

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Check that the connectors are properly connected to the occupant detection ECU and front occupant classification sensor LH.

   OK

   The connectors are properly connected.

   HINT: 

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

4. Disconnect the connectors from the occupant detection ECU and front occupant classification sensor LH.
5. Check that the terminals of the connectors are not deformed or damaged.

   OK

   The terminals are not deformed or damaged.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  2

1. Connect the cable to the negative (-) auxiliary battery terminal.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *1	Front Occupant Classification Sensor LH
   *2	Occupant Detection ECU
   *3	Front Seat Wire RH
   *4	Service Wire
   *a	Front view of wire harness connector (to Occupant Detection ECU)
   *b	Front view of wire harness connector (to Front Occupant Classification Sensor LH)

2. Turn the ignition switch to ON.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   e1-1 (SVC1) - Body ground	Ignition switch ON	Below 1 V
   e1-3 (SIG1) - Body ground	Ignition switch ON	Below 1 V
   e1-5 (SGD1) - Body ground	Ignition switch ON	Below 1 V

4. Turn the ignition switch off.
5. Disconnect the cable from the negative (-) auxiliary battery terminal.
6. Using service wires, connect terminals 1 (SVC) and 3 (SGD), and terminals 2 (SIG) and 3 (SGD) of connector C.
   NOTE:

   Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   e1-1 (SVC1) - e1-5 (SGD1)	Always	Below 1 Ω
   e1-3 (SIG1) - e1-5 (SGD1)	Always	Below 1 Ω

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   e1-1 (SVC1) - e1-5 (SGD1)	Always	1 MΩ or higher
   e1-3 (SIG1) - e1-5 (SGD1)	Always	1 MΩ or higher
   e1-1 (SVC1) - e1-3 (SIG1)	Always	1 MΩ or higher
   e1-1 (SVC1) - Body ground	Always	1 MΩ or higher
   e1-3 (SIG1) - Body ground	Always	1 MΩ or higher
   e1-5 (SGD1) - Body ground	Always	1 MΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  3

1. Connect the connectors to the occupant detection ECU and front occupant classification sensor LH.
2. Connect the cable to the negative (-) auxiliary battery terminal.
3. Turn the ignition switch to ON, and wait for at least 60 seconds.
4. Clear the DTCs stored in the occupant detection ECU.

   Body Electrical > Occupant Detection > Clear DTCs 

5. Clear the DTCs stored in the airbag sensor assembly.

   Body Electrical > SRS Airbag > Clear DTCs 

6. Turn the ignition switch off.
7. Turn the ignition switch to ON, and wait for at least 10 seconds.
8. Check for DTCs.

   Body Electrical > Occupant Detection > Trouble Codes 

   OK

   DTC B1780 is not output.

   HINT: 

   Codes other than DTC B1780 may be output at this time, but they are not related to this check.

9. Turn the ignition switch off.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ] 

Result: 

NG 

See step  4

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Replace the occupant detection ECU with a known good one.

   Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

   HINT: 

   Perform the following inspection using known good parts from another vehicle if possible.

3. Connect the cable to the negative (-) auxiliary battery terminal.
4. Turn the ignition switch to ON, and wait for at least 60 seconds.
5. Clear the DTCs stored in the occupant detection ECU.

   Body Electrical > Occupant Detection > Clear DTCs 

6. Clear the DTCs stored in the airbag sensor assembly.

   Body Electrical > SRS Airbag > Clear DTCs 

7. Turn the ignition switch off.
8. Turn the ignition switch to ON, and wait for at least 10 seconds.
9. Check for DTCs.

   Body Electrical > Occupant Detection > Trouble Codes 

   OK

   DTC B1780 is not output.

   HINT: 

   Codes other than DTC B1780 may be output at this time, but they are not related to this check.

10. Turn the ignition switch off.
11. Disconnect the cable from the negative (-) auxiliary battery terminal.
12. Restore the occupant detection ECU that was installed for testing to its original location.

    Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

    Result

    Proceed to
    OK
    NG

Result: 

NG 

See step  7

Result: 

OK 

See step  5

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Replace the occupant detection ECU with a new one.

   Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

4. Connect the cable to the negative (-) auxiliary battery terminal.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  6

1. Using the GTS, perform Zero Point Calibration.

   Refer to INITIALIZATION [12/2019 - 10/2021] , or refer to INITIALIZATION [10/2021 - 11/2023]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Replace the separate type front seat cushion spring assembly RH.

   for Manual Seat: Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

   for Power Seat: Refer to REMOVAL [12/2019 - 10/2021] , or refer to REMOVAL [10/2021 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

4. Connect the cable to the negative (-) auxiliary battery terminal.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  8

1. Using the GTS, perform Zero Point Calibration.

   Refer to INITIALIZATION [12/2019 - 10/2021] , or refer to INITIALIZATION [10/2021 - 11/2023]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END