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

1. Turn the ignition switch to ON.
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 ignition switch to OFF.
5. Turn the ignition switch to ON.
6. Check for the 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   15 

1. Turn the ignition switch to OFF.
2. Disconnect the negative (-) terminal cable from the battery, 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 

1. Connect the negative (-) terminal cable to the battery.
   Fig 1: Checking Occupant Classification System Circuit

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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
   M2-11 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   M2-12 (FSR-) - Body ground

4. Turn the ignition switch to OFF.
5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 second.
6. Using a service wire, connect terminals 12 (FSR+) and 13 (FSR-) of connector B.
   NOTE:

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

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

   Standard resistance

   Tester Connection	Condition	Specified Condition
   M2-11 (FSR+) - M2-12 (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
   M2-11 (FSR+) - M2-12 (FSR-)	Always	1 MΩ or higher
   M2-11 (FSR+) - Body ground
   M2-12 (FSR-) - Body ground

NG → See step   14 

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 negative (-) terminal cable to the battery.
4. Turn the ignition switch to ON.
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 ignition switch to OFF.
8. Turn the ignition switch to ON.
9. Using the Techstream, check for the 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   16 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Using the Techstream, save the ECU data from the ECU which was installed on the vehicle. Refer to REGISTRATION .

NEXT: Go to next step 

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

NEXT: Go to next step 

1. Turn the ignition switch to ON.
2. Using the Techstream, load the previous ECU data stored in the tester into the new ECU. Refer to REGISTRATION .

NEXT: Go to next step 

1. Using the Techstream, perform zero point calibration. Refer to INITIALIZATION .

NEXT: Go to next step 

HINT: 

Check that the zero point calibration is completed normally. If one of the following conditions is met, DTC B1797 will be output (refer to INITIALIZATION. Refer to INITIALIZATION ):

• Zero point calibration is performed when the conditions for the calibration are not satisfied.
• Zero point calibration has failed.

1. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
2. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
3. Turn the ignition switch to OFF.
4. Turn the ignition switch to ON.
5. Check for the DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

   Result

   Result	Proceed to
   No DTC output.	A
   DTC B1790 is output.	B
   DTC B1797 is output.	C

B → See step   12 

C → See step   17 

A: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

NEXT → END 

1. Turn the ignition switch to OFF.
2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
3. Replace the center airbag sensor. Refer to REMOVAL .
4. Connect the negative (-) terminal cable to the battery.

NEXT: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

NEXT → END 

Fig 2: Checking No. 2 Floor Wire

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the front seat wire RH connector from the No. 2 floor wire.
2. Connect the negative (-) terminal cable to the battery.
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
   IM1-5 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   IM1-10 (FSR-) - Body ground

5. Turn the ignition switch to OFF.
6. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
7. Using a service wire, connect terminals 12 (FSR+) and 13 (FSR-) of connector B.
   NOTE:

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

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

   Standard resistance

   Tester Connection	Condition	Specified Condition
   IM1-5 (FSR+) - IM1-10 (FSR-)	Always	Below 1 Ω

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

    Standard resistance

    Tester Connection	Condition	Specified Condition
    IM1-5 (FSR+) - IM1-10 (FSR-)	Always	1 MΩ or higher
    IM1-5 (FSR+) - Body ground
    IM1-10 (FSR-) - Body ground

NG → REPLACE NO. 2 FLOOR WIRE 

OK → REPLACE FRONT SEAT WIRE RH