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

1. Turn the engine switch on (IG).
2. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
3. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off.
5. Turn the engine switch on (IG).
6. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1790 is not output.

   HINT: 

   Codes 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   14 

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 classification ECU and the center airbag sensor.

   OK

   Connectors are properly connected.

NG → CONNECT CONNECTORS PROPERLY 

OK: Go to next step 

1. Disconnect the connectors from the center airbag sensor and the occupant classification ECU.
2. Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged.

   OK

   Connectors are not deformed or damaged.

NG → REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

Fig 1: Identifying Occupant Classification ECU Connector Terminal C8 And Center Airbag Sensor Connector Terminal L27

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
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
   c8-11 (FSR+) - Body ground	Engine switch on (IG)	Below 1 V
   c8-12 (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 16 (FSR+) and 22 (FSR-) of connector B.
   NOTE:

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   c8-11 (FSR+) - c8-12 (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
   c8-11 (FSR+) - c8-12 (FSR-)	Always	1 MΩ or higher
   c8-11 (FSR+) - Body ground
   c8-12 (FSR-) - Body ground

NG → See step   12 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and the center airbag sensor.
2. Connect the Techstream to the DLC3.
3. Connect the cable to the negative (-) battery terminal.
4. Turn the engine switch on (IG).
5. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
6. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
7. Turn the engine switch off.
8. Turn the engine switch on (IG).
9. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1790 is not output.

   HINT: 

   Codes 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. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Using the Techstream, save the ECU data from the ECU which is installed in the vehicle. Refer to REGISTRATION .
4. Turn the engine switch off.
5. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
6. Replace the No. 1 seat cushion (occupant classification ECU). Refer to DISASSEMBLY .
7. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
8. Turn the engine switch on (IG).
9. Using the Techstream, load the previous ECU data stored in the Techstream into the new ECU. Refer to REGISTRATION .
10. Turn the engine switch off.
11. Turn the engine switch on (IG).
12. Clear the DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

    HINT: 

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

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Using the Techstream, perform zero point calibration. Refer to INITIALIZATION .
4. Turn the engine switch off.
5. Turn the engine switch on (IG).
6. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   HINT: 

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

NEXT: Go to next step 

1. Turn the engine switch on (IG).
2. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
3. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off.
5. Turn the engine switch on (IG).
6. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1790 is not output.

   HINT: 

   Codes other than DTC B1790 may be output at this time, but they are not related to this check.

NG → See step   10 

OK: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

NEXT → END 

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 center airbag sensor. Refer to REMOVAL .

NEXT: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

NEXT → END 

Fig 2: Identifying Front Seat Wire RH Connector Terminal Lc2 And Center Airbag Sensor Connector Terminal L27

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Disconnect the front seat wire RH connector from the No. 2 floor wire.
4. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
5. Turn the engine switch on (IG).
6. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   Lc2-6 (FSR+) - Body ground	Engine switch on (IG)	Below 1 V
   Lc2-7 (FSR-) - Body ground

7. Turn the engine switch off.
8. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
9. Disconnect the front seat wire RH connector from the No. 2 floor wire.
10. Using service wire, connect terminals 16 (FSR+) and 22 (FSR-) of connector B.
    NOTE:

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

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

    Standard Resistance

    Tester Connection	Condition	Specified Condition
    Lc2-6 (FSR+) - Lc2-7 (FSR-)	Always	Below 1 Ω

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

    Standard Resistance

    Tester Connection	Condition	Specified Condition
    Lc2-6 (FSR+) - Lc2-7 (FSR-)	Always	1 MΩ or higher
    Lc2-6 (FSR+) - Body ground
    Lc2-7 (FSR-) - Body ground

NG → REPLACE NO. 2 FLOOR WIRE 

OK → REPLACE FRONT SEAT WIRE RH