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

   HINT: 

   • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
   • 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   12 

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 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: Go to next step 

1. Check that the connectors (on the center 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: Go to next step 

Fig 1: Checking Occupant Classification System Circuit

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 ignition switch to ON.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   M3-8 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   M3-4 (FSR-) - Body ground

4. Turn the ignition 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 24 (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
   M3-8 (FSR+) - M3-4 (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
   M3-8 (FSR+) - M3-4 (FSR-)	Always	1 MΩ or higher
   M3-8 (FSR+) - Body ground
   M3-4 (FSR-) - Body ground

NG → See step   11 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and the center airbag sensor assembly.
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 any DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   • First clear any DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
   • 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   13 

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.

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

NEXT: Go to next step 

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

   HINT: 

   • First clear any DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
   • 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   10 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

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 → END 

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 center airbag sensor assembly. Refer to REMOVAL .

   HINT: 

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

NEXT → END 

Fig 2: Checking Front Seat Wire RH

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the front seat wire RH connector from the floor wire.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the ignition switch to ON.
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   GM3-1 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   GM3-4 (FSR-) - Body ground

5. Turn the ignition switch off.
6. Disconnect the connector from the occupant classification ECU.
7. 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 connector.

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   GM3-1 (FSR+) - GM3-4 (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
    GM3-1 (FSR+) - GM3-4 (FSR-)	Always	1 MΩ or higher
    GM3-1 (FSR+) - Body ground
    GM3-4 (FSR-) - Body ground

NG → See step   14 

OK → REPLACE FLOOR WIRE