Dtc B1773 Belt Tension Sensor Circuit Malfunction

Vehicle Interior. Corolla. Zre142 Aze141
Supplemental Restraint Systems. Corolla. Zre142 Aze141

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK CONNECTORS

CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO B+)

CHECK SEAT BELT TENSION SENSOR CIRCUIT (OPEN)

CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO GROUND)

CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT)

CHECK FOR DTC

INSPECT FRONT SEAT OUTER BELT ASSEMBLY RH

REPLACE OCCUPANT CLASSIFICATION ECU

PERFORM SENSITIVITY CHECK

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

CHECK FRONT SEAT WIRE RH (OPEN)

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

CHECK FRONT SEAT WIRE RH (SHORT)

DTC B1773 Belt Tension Sensor Circuit Malfunction

DTC B1776 Seat Belt Tension Sensor Power Source Circuit Malfunction


DESCRIPTION

The seat belt tension sensor circuit consists of the occupant classification ECU and the seat belt tension sensor.
The seat belt tension sensor sends the seat belt tension signal to the occupant classification ECU.
DTC B1773 and B1776 are recorded when a malfunction is detected in the seat belt tension sensor circuit.

DTC No.
DTC Detecting Condition
Trouble Area
B1773
B1776
  1. The occupant classification ECU receives a short circuit signal, open circuit signal and short circuit to ground signal or a short circuit to B+ signal in the seat belt tension sensor circuit for 2 seconds.
  2. Seat belt tension sensor malfunction
  3. Occupant classification ECU malfunction
  1. No. 2 floor wire
  2. Front seat wire RH
  3. Front seat outer belt assembly RH (Seat belt tension sensor)
  4. Occupant classification ECU
HINT:
When DTC B1650/32 is detected as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant classification ECU. When DTC B1773 and B1776 are output, perform troubleshooting for those DTCs.

WIRING DIAGRAM


Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction


INSPECTION PROCEDURE

HINT:
  1. If troubleshooting (wire harness inspection) is difficult to perform, remove the passenger seat installation bolts to access the underside of the seat cushion.
  2. In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may damage the seat or deform the seat rails. Hold the seat only as necessary.
1.CHECK CONNECTORS

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal.

  1. Check that the connectors are properly connected to the occupant classification ECU and the seat belt tension sensor.

    OK:
    The connectors are properly connected.
    HINT:
    If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

  1. Disconnect the connectors from the occupant classification ECU and the seat belt tension sensor.

  1. Check that the terminals of the connectors are not damaged.

    OK:
    The terminals are not deformed or damaged.


NG
REPLACE WIRE HARNESS
OK


2.CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO B+)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

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

  1. Turn the ignition switch to ON.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    R2-8 (GBT) - Body ground
    		Ignition switch ON
    		Below 1 V
    R2-16 (BT) - Body ground
    		Ignition switch ON
    		Below 1 V
    R2-17 (VBT) - Body ground
    		Ignition switch ON
    		Below 1 V


NG
Go to step 10
OK


3.CHECK SEAT BELT TENSION SENSOR CIRCUIT (OPEN)


  1. Turn the ignition switch off.


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Disconnect the cable from the negative (-) battery terminal.

  1. Using SST, connect terminals 1 (GBT) and 3 (BT), and connect terminals 2 (VBT) and 3 (BT) of connector E.

    NOTICE:
    Do not forcibly insert SST into the terminals of the connector when connecting the wire.
SST
09843-18040

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-16 (BT) - R2-8 (GBT)
    		Always
    		Below 1 Ω
    R2-17 (VBT) - R2-16 (BT)
    		Always
    		Below 1 Ω


NG
Go to step 11
OK


4.CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO GROUND)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Disconnect SST from connector E.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-8 (GBT) - Body ground
    		Always
    		1 MΩ or higher
    R2-16 (BT) - Body ground
    		Always
    		1 MΩ or higher
    R2-17 (VBT) - Body ground
    		Always
    		1 MΩ or higher


NG
Go to step 12
OK


5.CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-16 (BT) - R2-8 (GBT)
    		Always
    		1 MΩ or higher
    R2-17 (VBT) - R2-16 (BT)
    		Always
    		1 MΩ or higher


NG
Go to step 13
OK


6.CHECK FOR DTC

  1. Connect the connectors to the occupant classification ECU and the seat belt tension sensor.

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

  1. Turn the ignition switch to ON.

  1. Clear the DTCs stored in the occupant classification ECU (COROLLA_ZRE142 RM0000010VK07TX.html).

  1. Clear the DTCs stored in the center airbag sensor assembly (COROLLA_ZRE142 RM000000XFE0H1X.html).

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON.

  1. Check for DTCs (COROLLA_ZRE142 RM0000010VK07TX.html).

    OK:
    DTC B1773 and B1776 are not output.
    HINT:
    Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.


NG
Go to step 7
OK

USE SIMULATION METHOD TO CHECK (COROLLA_ZRE142 RM000000XFD0GSX.html)

7.INSPECT FRONT SEAT OUTER BELT ASSEMBLY RH

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal.

  1. Replace the front seat outer belt assembly RH with a known good part (COROLLA_ZRE142 RM00000120B077X.html).

    HINT:
    Perform an inspection using known good parts from another vehicle if possible.

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

  1. Turn the ignition switch to ON.

  1. Clear the DTCs stored in the occupant classification ECU (COROLLA_ZRE142 RM0000010VK07TX.html).

  1. Clear the DTCs stored in the center airbag sensor assembly (COROLLA_ZRE142 RM000000XFE0H1X.html).

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON.

  1. Check for DTCs (COROLLA_ZRE142 RM0000010VK07TX.html).

    OK:
    DTC B1773 and B1776 are not output.
    HINT:
    Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.


NG
Go to step 8
OK

END

8.REPLACE OCCUPANT CLASSIFICATION ECU

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Using the Techstream, save the ECU data from the ECU currently installed on the vehicle (COROLLA_ZRE142 RM000001QX402OX.html).

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal.

  1. Replace the occupant classification ECU (COROLLA_ZRE142 RM0000011JG03CX.html).

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

  1. Turn the ignition switch to ON.

  1. Using the Techstream, load the previous ECU data stored into the new ECU (COROLLA_ZRE142 RM000001QX402OX.html).

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON.

  1. Clear the DTCs stored in the memory (COROLLA_ZRE142 RM0000010VK07TX.html).

    HINT:
    If the DTCs are not cleared at this time, past DTCs will remain.

NEXT


9.PERFORM SENSITIVITY CHECK

  1. Perform the sensitivity check (COROLLA_ZRE142 RM0000010VN07SX.html).


NEXT

END

10.CHECK FRONT SEAT WIRE RH (SHORT TO B+)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal.

  1. Disconnect the No. 2 floor wire connector from the front seat wire RH.

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

  1. Turn the ignition switch to ON.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    R2-8 (GBT) - Body ground
    		Ignition switch ON
    		Below 1 V
    R2-16 (BT) - Body ground
    		Ignition switch ON
    		Below 1 V
    R2-17 (VBT) - Body ground
    		Ignition switch ON
    		Below 1 V


NG
REPLACE FRONT SEAT WIRE RH
OK

REPLACE NO. 2 FLOOR WIRE

11.CHECK FRONT SEAT WIRE RH (OPEN)


  1. Disconnect the No. 2 floor wire connector from the front seat wire RH.


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Using SST, connect terminals 4 (BT) and 8 (GBT), and connect terminals 4 (BT) and 9 (VBT) of connector C.

    NOTICE:
    Do not forcibly insert SST into the terminals of the connector when connecting the wire.
SST
09843-18040

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-16 (BT) - R2-8 (GBT)
    		Always
    		Below 1 Ω
    R2-16 (BT) - R2-17 (VBT)
    		Always
    		Below 1 Ω


NG
REPLACE FRONT SEAT WIRE RH
OK

REPLACE NO. 2 FLOOR WIRE

12.CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Disconnect the No. 2 floor wire connector from the front seat wire RH.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-8 (GBT) - Body ground
    		Always
    		1 MΩ or higher
    R2-16 (BT) - Body ground
    		Always
    		1 MΩ or higher
    R2-17 (VBT) - Body ground
    		Always
    		1 MΩ or higher


NG
REPLACE FRONT SEAT WIRE RH
OK

REPLACE NO. 2 FLOOR WIRE

13.CHECK FRONT SEAT WIRE RH (SHORT)


    Corolla. Zre142 Aze141.Supplemental Restraint Systems.Airbag System. Dtc B1773 Belt Tension Sensor Circuit Malfunction

  1. Disconnect the No. 2 floor wire connector from the front seat wire RH.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    R2-16 (BT) - R2-8 (GBT)
    		Always
    		1 MΩ or higher
    R2-17 (VBT) - R2-16 (BT)
    		Always
    		1 MΩ or higher


NG
REPLACE FRONT SEAT WIRE RH
OK

REPLACE NO. 2 FLOOR WIRE