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

WARNING: This page is about a different car, the 2010 Toyota FJ Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

CHECK DTC
1. Turn the ignition switch to the on position.
2. Clear the DTCs stored in the memory. Refer toDTC CHECK / CLEAR .
  HINT:
  
  First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
3. Turn the ignition switch to the lock position.
4. Turn the ignition switch to the on position.
5. Check the DTCs. Refer toDTC CHECK / CLEAR .
  OK
  
  DTC B1781 is not output.
  
  HINT:
  
  Codes other than DTC B1781 may be output at this time, but they are not related to this check.
OK → See step 15

NG: Go to next step
CHECK CONNECTION OF CONNECTORS
1. Turn the ignition switch to the lock position.
2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
3. Check that the connectors are properly connected to the occupant classification ECU and the front occupant classification sensor RH.
  OK
  
  The connectors are properly connected.
NG → CONNECT CONNECTORS

OK: Go to next step

CHECK NO. 1 SEAT WIRE (TO B+)

Disconnect the connectors from the occupant classification ECU and the front occupant classification sensor RH.

Fig 1: Identifying Front Occupant Classification Sensor RH, No. 1 Seat Wire (To B+) & Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Connect the negative (-) terminal cable to the battery.
Turn the ignition switch to the on position.

Measure the voltage.

Standard voltage

Tester connection	Condition	Specified condition
Q5-2 (SGD2) - Body ground	Ignition switch on	Below 1 V
Q5-8 (SIG2) - Body ground	Ignition switch on	Below 1 V
Q5-12 (SVC2) - Body ground	Ignition switch on	Below 1 V

NG → REPAIR OR REPLACE NO. 1 SEAT WIRE

OK: Go to next step

CHECK NO. 1 SEAT WIRE (FOR OPEN)

Turn the ignition switch to the lock position.

Fig 2: Identifying Front Occupant Classification Sensor RH, No. 1 Seat Wire (For Open) & Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
Using a service wire, connect Q7-1 (SVC2) and Q7-3 (SGD2), and connect Q7-2 (SIG2) and Q7-3 (SGD2) of connector C.
NOTE:
Do not forcibly insert a service wire into the terminals of the connector when connecting.

Measure the resistance.

Standard resistance

Tester connection	Condition	Specified condition
Q5-8 (SIG2) - Q5-2 (SGD2)	Always	Below 1 Ω
Q5-12 (SVC2) - Q5-2 (SGD2)	Always	Below 1 Ω

NG → REPAIR OR REPLACE NO. 1 SEAT WIRE

OK: Go to next step

CHECK NO. 1 SEAT WIRE (FOR SHORT)

Disconnect the service wire from connector C.

Fig 3: Identifying Front Occupant Classification ECU, Sensor, No. 1 Seat Wire (For Short) & Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Measure the resistance.

Standard resistance

Tester connection	Condition	Specified condition
Q5-8 (SIG2) - Q5-2 (SGD2)	Always	1 MΩ or higher
Q5-12 (SVC2) - Q5-2 (SGD2)	Always	1 MΩ or higher
Q5-8 (SIG2) - Q5-12 (SVC2)	Always	1 MΩ or higher

NG → REPAIR OR REPLACE NO. 1 SEAT WIRE

OK: Go to next step

CHECK NO. 1 SEAT WIRE (TO GROUND)

Measure the resistance.

Fig 4: Identifying Front Occupant Classification Sensor, No. 1 Seat Wire (For Short) & Connector Terminals

Standard resistance

Tester connection	Condition	Specified condition
Q5-2 (SGD2) - Body ground	Always	1 MΩ or higher
Q5-8 (SIG2) - Body ground	Always	1 MΩ or higher
Q5-12 (SVC2) - Body ground	Always	1 MΩ or higher

NG → REPAIR OR REPLACE NO. 1 SEAT WIRE

OK: Go to next step

CHECK DTC
1. Connect the connectors to the occupant classification ECU and the front occupant classification sensor RH.
2. Connect the negative (-) terminal cable to the battery.
3. Turn the ignition switch to the on position.
4. Clear the DTCs stored in the memory. Refer toDTC CHECK / CLEAR .
  HINT:
  
  First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
5. Turn the ignition switch to the lock position.
6. Turn the ignition switch to the on position.
7. Check the DTCs. Refer toDTC CHECK / CLEAR .
  OK
  
  DTC B1781 is not output.
  
  HINT:
  
  Codes other than DTC B1781 may be output at this time, but they are not related to this check.
OK → See step 15

NG: Go to next step
REPLACE OCCUPANT CLASSIFICATION ECU
1. Turn the ignition switch to the lock position.
2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
3. Replace the occupant classification ECU. Refer toREMOVAL .
  HINT:
  
  Perform the inspection using parts from a normal vehicle if possible.
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the negative (-) terminal cable to the battery.
2. Connect a Techstream to the DLC3.
3. Turn the ignition switch to the on position.
4. Using the Techstream, perform the zero point calibration. Refer toINITIALIZATION .
  OK
  
  COMPLETED is displayed.
NG → See step 12

OK: Go to next step
PERFORM SENSITIVITY CHECK
1. Using a Techstream, perform the sensitivity check. Refer toINITIALIZATION .
  1. Confirm that nothing is placed on the passenger seat.
  2. Confirm that the beginning sensor reading is within the standard range.
    Standard range
    
    -3.2 to 3.2 kg (-7 to 7 lb)
  3. Place a 30 kg (66.14 lb) weight (e.g. a lead mass) onto the front passenger seat.
  4. Confirm that the sensitivity is within the standard range.
    Standard range
    
    27 to 33 kg (59.52 to 72.75 lb)
    
    HINT:
    
    When performing the sensitivity check, use a solid metal weight (the check result may not be accurate if a liquid weight is used).
NG → See step 12

OK: Go to next step
CHECK DTC
1. Connect the negative (-) terminal cable to the battery.
2. Turn the ignition switch to the on position.
3. Clear the DTCs stored in the memory. Refer toDTC CHECK / CLEAR .
  HINT:
  
  First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
4. Turn the ignition switch to the lock position.
5. Turn the ignition switch to the on position.
6. Check the DTCs. Refer toDTC CHECK / CLEAR .
  OK
  
  DTC B1781 is not output.
  
  HINT:
  
  Codes other than DTC B1781 may be output at this time, but they are not related to this check.
OK → END

NG: Go to next step
REPLACE FRONT SEAT ASSEMBLY RH
1. Turn the ignition switch to the lock position.
2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
3. Replace the front seat assembly RH. Refer toREMOVAL .
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the negative (-) terminal cable to the battery.
2. Connect a Techstream to the DLC3.
3. Turn the ignition switch to the on position.
4. Using the Techstream, perform the zero point calibration. Refer toINITIALIZATION .
  OK
  
  COMPLETED is displayed.
NEXT: Go to next step
PERFORM SENSITIVITY CHECK
1. Using a Techstream, perform the sensitivity check. Refer toINITIALIZATION .
  1. Confirm that nothing is placed on the passenger seat.
  2. Confirm that the beginning sensor reading is within the standard range.
    Standard range
    
    -3.2 to 3.2 kg (-7 to 7 lb)
  3. Place a 30 kg (66.14 lb) weight (e.g. a lead mass) onto the front passenger seat.
  4. Confirm that the sensitivity is within the standard range.
    Standard range
    
    27 to 33 kg (59.52 to 72.75 lb)
    
    HINT:
    
    When performing the sensitivity check, use a solid metal weight (the check result may not be accurate if a liquid weight is used).
NEXT → END
USE SIMULATION METHOD TO CHECK. Refer to DIAGNOSIS SYSTEM