DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction: Procedure

1. Turn the ignition switch to ON, and wait for at least 60 seconds.
2. Clear the DTCs stored in memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
3. Turn the ignition switch off.
4. Turn the ignition switch to ON, and wait for at least 60 seconds.
5. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   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 → See step   2 

OK → See step   11 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Check that the connectors are properly connected to the occupant classification ECU and center airbag sensor.

   OK

   Connectors are properly connected.

NG → CONNECT CONNECTOR 

OK: Go to next step 

1. Disconnect the connectors from the center airbag sensor and occupant classification ECU.
2. Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

   OK

   Connectors are not deformed or damaged.

NG → REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
   Fig 1: Identifying Occupant Classification System Circuit Wiring Diagram

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

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   a9-8 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   a9-4 (FSR-) - Body ground

3. Turn the ignition switch off.
4. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
5. Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.
   NOTE:

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   a9-8 (FSR+) - a9-4 (FSR-)	Always	Below 1 Ω

7. Disconnect the service wire from connector B.
8. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   a9-8 (FSR+) - a9-4 (FSR-)	Always	1 MΩ or higher
   a9-8 (FSR+) - Body ground
   a9-4 (FSR-) - Body ground

   TEXT IN ILLUSTRATION
   
   

   *1	Occupant Classification ECU
   *2	Center Airbag Sensor
   *3	Service Wire
   *4	Connector E
   *5	Connector B
   *a	Front view of wire harness connector (to Occupant Classification ECU)
   *b	Front view of wire harness connector (to Center Airbag Sensor)

NG → See step   10 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and center airbag sensor.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the ignition switch to ON, and wait for at least 60 seconds.
4. Clear the DTCs stored in memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
5. Turn the ignition switch off.
6. Turn the ignition switch to ON, and wait for at least 60 seconds.
7. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   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 → See step   6 

OK → See step   12 

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the occupant classification ECU. Refer to REMOVAL .

   HINT: 

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

NEXT: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Turn the ignition switch to ON, and wait for at least 60 seconds.
3. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

   OK

   "Zero Point Calibration is complete." is displayed.

NEXT: Go to next step 

1. Using the Techstream, perform the sensitivity check. Refer to INITIALIZATION .

   Standard range

   27 to 33 kg (59.5 to 72.8 lb)

NEXT: Go to next step 

1. Clear the DTCs stored in memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
2. Turn the ignition switch off.
3. Turn the ignition switch to ON, and wait for at least 60 seconds.
4. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   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 → See step   13 

OK → END 

1. Disconnect the front seat wire RH connector from the floor wire.
   Fig 2: Identifying Front Seat Wire RH Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   Na2-1 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   Na2-4 (FSR-) - Body ground

4. Turn the ignition switch off.
5. Disconnect the connector from the occupant classification ECU.
6. Using a service wire, connect terminals 8 (FSR+) and 4 (FSR-) of connector E.
   NOTE:

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Na2-1 (FSR+) - Na2-4 (FSR-)	Always	Below 1 Ω

8. Disconnect the service wire from connector E.
9. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Na2-1 (FSR+) - Na2-4 (FSR-)	Always	1 MΩ or higher
   Na2-1 (FSR+) - Body ground
   Na2-4 (FSR-) - Body ground

   TEXT IN ILLUSTRATION
   
   

   *1	Front Seat Wire RH
   *2	Floor Wire
   *3	Occupant Classification ECU
   *4	Center Airbag Sensor
   *5	Service Wire
   *6	Connector E
   *7	Connector D
   *a	Front view of wire harness connector (to Occupant Classification ECU)
   *b	Front view of wire harness connector (to Front Seat Wire RH)

NG → REPLACE FRONT SEAT WIRE RH 

OK → REPLACE FLOOR WIRE