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

CHECK CONNECTORS
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Check that the connectors are properly connected to the occupant classification 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 classification ECU and front occupant classification sensor LH.
5. Check that the terminals of connectors are not damaged.
  OK
  
  The terminals are not deformed or damaged.
NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

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

Fig 1: Front Seat Wire RH
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Turn the engine switch on (IG).

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

Standard Voltage

Tester Connection	Condition	Specified Condition
Z1-1 (SGD1) - Body ground	Engine switch on (IG)	Below 1 V
Z1-7 (SIG1) - Body ground	Engine switch on (IG)	Below 1 V
Z1-11 (SVC1) - Body ground	Engine switch on (IG)	Below 1 V

TEXT IN ILLUSTRATION

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

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (OPEN)

Turn the engine switch off.

Fig 2: Front Seat Wire RH
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the cable from the negative (-) battery terminal.
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

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

Standard Resistance

Tester Connection	Condition	Specified Condition
Z1-7 (SIG1) - Z1-1 (SGD1)	Always	Below 1 Ω
Z1-11 (SVC1) - Z1-1 (SGD1)	Always	Below 1 Ω

TEXT IN ILLUSTRATION

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

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT)

Disconnect SST from connector C.

Fig 3: Front Seat Wire RH
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

Standard Resistance

Tester Connection	Condition	Specified Condition
Z1-7 (SIG1) - Z1-1 (SGD1)	Always	1 MΩ or higher
Z1-11 (SVC1) - Z1-1 (SGD1)	Always	1 MΩ or higher
Z1-7 (SIG1) - Z1-11 (SVC1)	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

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

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

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

Fig 4: Front Seat Wire RH

Standard Resistance

Tester Connection	Condition	Specified Condition
Z1-1 (SGD1) - Body ground	Always	1 MΩ or higher
Z1-7 (SIG1) - Body ground	Always	1 MΩ or higher
Z1-11 (SVC1) - Body ground	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

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

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK DTC
1. Connect the connectors to the occupant classification ECU and front occupant classification sensor LH.
2. Connect the cable to the negative (-) battery terminal.
3. Turn the engine switch on (IG).
4. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
5. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
6. Turn the engine switch off.
7. Turn the engine 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 14
REPLACE OCCUPANT CLASSIFICATION ECU
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Replace the occupant classification ECU. Refer to REMOVAL .
  HINT:
  
  Perform the inspection using parts from a normal vehicle if possible.
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) battery terminal.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG).
4. Using the Techstream, perform Zero Point Calibration. Refer to INITIALIZATION .
  OK
  
  "Zero Point Calibration is complete." is displayed.
NG → See step 11

OK: Go to next step
PERFORM SENSITIVITY CHECK
1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION .
  Standard
  
  27 to 33 kg (59.5 to 72.8 lb)
NG → See step 11

OK: Go to next step
CHECK DTC
1. Turn the engine switch on (IG).
2. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
3. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off.
5. Turn the engine switch on (IG).
6. 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 11

OK → END
REPLACE FRONT SEAT ASSEMBLY RH*1 OR FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH*2
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Replace the front seat assembly RH*1 or front seat frame with adjuster assembly RH*2. Refer to REMOVAL .
  *1: for TMMC Made
  
  *2: for TMC Made
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) battery terminal.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG).
4. Using the Techstream, perform Zero Point Calibration. Refer to INITIALIZATION .
  OK
  
  "Zero Point Calibration is complete." is displayed.
NEXT: Go to next step
PERFORM SENSITIVITY CHECK
1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION .
  Standard
  
  27 to 33 kg (59.5 to 72.8 lb)
NEXT → END
USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING