DTC B1780: Front Occupant Classification Sensor LH Circuit Malfunction: Procedure

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 occupant detection ECU and front occupant classification sensor LH.

   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 occupant detection ECU and front occupant classification sensor LH.
5. Check that the terminals of the connectors are not damaged.

   OK

   The terminals are not deformed or damaged.

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the cable to the negative (-) auxiliary battery terminal.
   Fig 1: Identifying W3 Connector Terminals

   Courtesy 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
   W3-1 (SGD1) - Body ground	Power switch on (IG)	Below 1 V
   W3-7 (SIG1) - Body ground	Power switch on (IG)	Below 1 V
   W3-11 (SVC1) - Body ground	Power switch on (IG)	Below 1 V

   TEXT IN ILLUSTRATION
   
   

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

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Turn the power switch off.
   Fig 2: Identifying W3 And W6 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Using SST, connect terminals 1 (SVC1) and 3 (SGD1), and connect terminals 2 (SIG1) and 3 (SGD1) of connector C.
   NOTE:

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

   • SST: 09843-18040 
4. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W3-7 (SIG1) - W3-1 (SGD1)	Always	Below 1 Ω
   W3-11 (SVC1) - W3-1 (SGD1)	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

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

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Disconnect SST from connector C.
   Fig 3: Identifying W3 Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W3-7 (SIG1) - W3-1 (SGD1)	Always	1 MΩ or higher
   W3-11 (SVC1) - W3-1 (SGD1)	Always	1 MΩ or higher
   W3-7 (SIG1) - W3-11 (SVC1)	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

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

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 4: Identifying W3 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W3-1 (SGD1) - Body ground	Always	1 MΩ or higher
   W3-7 (SIG1) - Body ground	Always	1 MΩ or higher
   W3-11 (SVC1) - Body ground	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

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

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

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 power switch on (IG).
4. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR .
5. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR .
6. Turn the power switch off.
7. Turn the power switch on (IG).
8. Check for DTCs. Refer to DTC CHECK / CLEAR .

   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.

NG → See step   7 

OK → See step   10 

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 for Manual seat. Refer to DISASSEMBLY for Power seat).

NEXT: Go to next step 

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 .

NEXT: Go to next step 

1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION .

NEXT → END