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

1. Turn the ignition switch 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.
   • Use a 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 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   10 

1. Turn the ignition switch 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 CONNECTOR 

OK: Go to next step 

1. 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 FLOOR WIRE 

OK: Go to next step 

Fig 1: Measuring Voltage Of L27 & L11 Connectors

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
2. Turn the ignition switch ON, and wait for at least 60 seconds.
3. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connection	Switch Condition	Specified Condition
   L27-8 (FSR+) - Body ground	Ignition switch ON	Below 1 V
   L27-4 (FSR-) - Body ground

4. Turn the ignition switch off.
5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
6. Using a service wire, connect terminals 12 (FSP+) and 13 (FSP-) 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
   L27-8 (FSR+) - L27-4 (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
   L27-8 (FSR+) - L27-4 (FSR-)	Always	1 MΩ or higher
   L27-8 (FSR+) - Body ground
   L27-4 (FSR-) - Body ground

NG → REPLACE FLOOR WIRE 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and the center airbag sensor.
2. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
3. Turn the ignition switch 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.
   • Use a 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 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   11 

1. Turn the ignition switch 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 .

   HINT: 

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

NEXT: Go to next step 

1. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
2. Connect a Techstream to the DLC3.
3. Turn the ignition switch ON, and wait for at least 60 seconds.
4. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

NEXT: Go to next step 

1. Using a 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. Connect the connector to the occupant classification ECU.
2. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
3. Turn the ignition switch ON, and wait for at least 60 seconds.
4. 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.
   • Use a 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 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   12 

OK → END