Dtc B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction

Vehicle Interior. Yaris. Ncp93, 131
Supplemental Restraint Systems. Yaris. Ncp93, 131

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK FOR DTC

CHECK CONNECTION OF CONNECTOR

CHECK CONNECTOR

CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT

CHECK FOR DTC

REPLACE OCCUPANT CLASSIFICATION ECU

CHECK FOR DTC

PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK

REPLACE AIRBAG SENSOR ASSEMBLY

CHECK FRONT SEAT WIRE RH

DTC B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction


DESCRIPTION

The airbag sensor assembly communication circuit consists of the occupant classification ECU and the airbag sensor assembly.
DTC B1790 is stored when a malfunction is detected in the airbag sensor assembly communication circuit.

DTC Code
DTC Detection Condition
Trouble Area
B1790
One of following conditions is met:
  1. Occupant classification ECU receives line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in airbag sensor assembly communication circuit for 2 seconds
  2. Airbag sensor assembly malfunction
  3. Occupant classification ECU malfunction
  1. Floor wire
  2. Front seat wire RH
  3. Occupant classification ECU
  4. Airbag sensor assembly
HINT:
  1. When DTC B1650/32 is detected as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1790 of the occupant classification system.
  2. Use the Techstream to check for DTCs of the occupant classification ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM


Yaris. Ncp93, 131.Supplemental Restraint Systems.Airbag System (For Sedan). Dtc B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction


INSPECTION PROCEDURE

HINT:
  1. If troubleshooting (wire harness inspection) is difficult to perform, remove the front seat assembly RH installation bolts to see the undersurface 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 cause problems, such as seat rail deformation. Hold the seat up only for as long as necessary.
1.CHECK FOR DTC

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Clear any DTCs stored in the memory (YARIS_NCP93 RM0000010VK072X.html).

    HINT:
    1. First clear DTCs stored in the occupant classification ECU and then in the airbag sensor assembly.
    2. Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Using the Techstream, check for DTCs of the occupant classification ECU (YARIS_NCP93 RM0000010VK072X.html).

    OK:
    DTC B1790 is not output.
    HINT:
    DTCs other than DTC B1790 may be output at this time, but they are not related to this check.


NG
Go to step 2
OK

USE SIMULATION METHOD TO CHECK (YARIS_NCP93 RM0000010VJ076X.html)

2.CHECK CONNECTION OF CONNECTOR

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

  1. Check that the connectors are properly connected to the occupant classification ECU and airbag sensor assembly. Also check that the connectors that link the front seat wire RH and floor wire are properly connected.

    OK:
    Connectors are properly connected.


NG
CONNECT CONNECTORS PROPERLY
OK


3.CHECK CONNECTOR

  1. Check that the connectors (on the airbag sensor assembly side, occupant classification ECU side, front seat wire RH side and floor wire side) are not damaged.

    OK:
    Connectors are not deformed or damaged.


NG
REPLACE HARNESS OR CONNECTOR
OK


4.CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT

Yaris. Ncp93, 131.Supplemental Restraint Systems.Airbag System (For Sedan). Dtc B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction


Text in Illustration
*A
with VSC/Built-in Type Yaw Rate Sensor
*B
with VSC/Separate Type Yaw Rate Sensor without VSC
*1
Occupant Classification ECU
*2
Airbag Sensor Assembly
*3
Service Wire
-
-
*a
Front view of wire harness connector
(to Occupant Classification ECU)
*b
Rear view of wire harness connector
(to Airbag Sensor Assembly)
*c
Connector E
*d
Connector B

  1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

  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
    X4-7 - Body ground
    		Ignition switch ON
    		Below 1 V
    X4-4 - Body ground

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

  1. with VSC/Built-in Type Yaw Rate Sensor:

    1. Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.

      NOTICE:
      Do not forcibly insert the service wire into the terminals of the connector.

  1. with VSC/Separate Type Yaw Rate Sensor without VSC:

    1. Using a service wire, connect terminals 12 (FSR+) and 13 (FSR-) of connector B.

      NOTICE:
      Do not forcibly insert the service wire into the terminals of the connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    X4-7 - X4-4
    		Always
    		Below 1 Ω

  1. Disconnect the service wire from connector B.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    X4-7 - X4-4
    		Always
    		1 MΩ or higher
    X4-7 - Body ground
    X4-4 - Body ground


NG
Go to step 10
OK


5.CHECK FOR DTC

  1. Connect the connectors to the occupant classification ECU and the airbag sensor assembly.

  1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Clear any DTCs stored in the memory (YARIS_NCP93 RM0000010VK072X.html).

    HINT:
    1. First clear any DTCs stored in the occupant classification ECU and then in the airbag sensor assembly.
    2. Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Using the Techstream, check for DTCs of the occupant classification ECU (YARIS_NCP93 RM0000010VK072X.html).

    OK:
    DTC B1790 is not output.
    HINT:
    DTCs other than DTC B1790 may be output at this time, but they are not related to this check.


NG
Go to step 6
OK

USE SIMULATION METHOD TO CHECK (YARIS_NCP93 RM0000010VJ076X.html)

6.REPLACE OCCUPANT CLASSIFICATION ECU

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

  1. Replace the occupant classification ECU (YARIS_NCP93 RM0000011JG02SX.html).

    HINT:
    Perform the inspection using parts from a normal vehicle when possible.

  1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.


NEXT


7.CHECK FOR DTC

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Clear any DTCs stored in the memory (YARIS_NCP93 RM0000010VK072X.html).

    HINT:
    1. First clear any DTCs stored in the occupant classification ECU and then in the airbag sensor assembly.
    2. Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.

  1. Turn the ignition switch off.

  1. Turn the ignition switch to ON, and wait for at least 60 seconds.

  1. Using the Techstream, check for DTCs of the occupant classification ECU (YARIS_NCP93 RM0000010VK072X.html).

    OK:
    DTC B1790 is not output.
    HINT:
    DTCs other than DTC B1790 may be output at this time, but they are not related to this check.


NG
Go to step 9
OK


8.PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Using the Techstream, perform Zero Point Calibration and Sensitivity Check (YARIS_NCP93 RM0000010VN073X.html).


NEXT

END (OCCUPANT CLASSIFICATION ECU WAS DEFECTIVE)

9.REPLACE AIRBAG SENSOR ASSEMBLY

  1. Turn the ignition switch off.

  1. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

  1. Replace the airbag sensor assembly (YARIS_NCP93 RM000000V6U02AX.html).

    HINT:
    Perform the inspection using parts from a normal vehicle when possible.

NEXT

END

10.CHECK FRONT SEAT WIRE RH

Yaris. Ncp93, 131.Supplemental Restraint Systems.Airbag System (For Sedan). Dtc B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction


Text in Illustration
*1
Occupant Classification ECU
*2
Airbag Sensor Assembly
*3
Front Seat Wire RH
*4
Floor Wire
*5
Service Wire
-
-
*a
Front view of wire harness connector
(to Occupant Classification ECU)
*b
Front view of wire harness connector
(to Floor Wire)
*c
Connector E
*d
Connector D

  1. Disconnect the front seat wire RH connector from the floor wire.

  1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

  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
    JX1-1 - Body ground
    		Ignition switch ON
    		Below 1 V
    JX1-5 - Body ground

  1. Turn the ignition switch off.

  1. Disconnect the connector from the occupant classification ECU.

  1. Using a service wire, connect terminals 7 and 4 of connector E.

    NOTICE:
    Do not forcibly insert the service wire into the terminals of connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    JX1-1 - JX1-5
    		Always
    		Below 1 Ω

  1. Disconnect the service wire from connector E.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    JX1-1 - JX1-5
    		Always
    		1 MΩ or higher
    JX1-1 - Body ground
    JX1-5 - Body ground


NG
REPLACE FRONT SEAT WIRE RH (YARIS_NCP93 RM000001WB001FX.html)
OK

REPLACE FLOOR WIRE