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

1. Turn the engine switch on (IG), and wait for at least 60 seconds.
2. Clear the DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   HINT: 

   • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.
3. Turn the engine switch off.
4. Turn the engine switch on (IG), and wait for at least 60 seconds.
5. Check for DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   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 engine 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 detection 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 detection ECU.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Check that the connectors (on the center airbag sensor side and occupant detection ECU side) are not damaged. Refer to DIAGNOSIS SYSTEM [12/2011 - ] .

   OK

   Connectors are not deformed or damaged.

   TEXT IN ILLUSTRATION
   
   

   *1	Occupant Detection ECU
   *2	Center Airbag Sensor Assembly

NG → REPLACE HARNESS AND CONNECTOR 

OK: Go to next step 

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

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   z12-7 (FSR+) - Body ground	Engine switch on (IG)	Below 1 V
   z12-4 (FSR-) - Body ground

4. Turn the engine switch off.
5. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
6. Using a service wire, connect terminals 9 (FSR+) and 17 (FSR-) of connector B.
   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
   z12-7 (FSR+) - z12-4 (FSR-)	Always	Below 1 Ω

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   z12-7 (FSR+) - z12-4 (FSR-)	Always	1 MΩ or higher
   z12-7 (FSR+) - Body ground
   z12-4 (FSR-) - Body ground

   TEXT IN ILLUSTRATION
   
   

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

NG → See step   10 

OK: Go to next step 

1. Connect the connectors to the occupant detection ECU and center airbag sensor.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   HINT: 

   • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.
5. Turn the engine switch off.
6. Turn the engine switch on (IG), and wait for at least 60 seconds.
7. Check for DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   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   13 

1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the occupant detection ECU. Refer to REMOVAL [12/2011 - ] .

   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 engine switch on (IG).
3. Perform the zero point calibration. Refer to INITIALIZATION [12/2011 - ] .

   OK

   "Zero Point Calibration is complete." is displayed.

NEXT: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION [12/2011 - ] .

   Standard

   27 to 33 kg (59.5 to 72.8 lb)

NEXT: Go to next step 

1. Clear the DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   HINT: 

   • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
   • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.
2. Turn the engine switch off.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Check for DTCs. Refer to DTC CHECK / CLEAR [12/2011 - ] .

   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   12 

OK → END (OCCUPANT DETECTION ECU WAS DEFECTIVE) 

1. Disconnect the front seat inner belt assembly RH connector from the floor wire.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the engine switch on (IG).
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   T4-1 (FSR+) - Body ground	Engine switch on (IG)	Below 1 V
   T4-4 (FSR-) - Body ground

5. Turn the engine switch off.
6. Disconnect the connector from the occupant detection ECU.
7. Using a service wire, connect terminals 7 (FSR+) and 4 (FSR-) of connector E.
   NOTE:

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   T4-1 (FSR+) - T4-4 (FSR-)	Always	Below 1 Ω

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

    Standard Resistance

    Tester Connection	Condition	Specified Condition
    T4-1 (FSR+) - T4-4 (FSR-)	Always	1 MΩ or higher
    T4-1 (FSR+) - Body ground
    T4-4 (FSR-) - Body ground

    TEXT IN ILLUSTRATION
    
    

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

NG → See step   14 

OK → REPLACE FLOOR WIRE