DTC B1771: Passenger Side Buckle Switch Circuit Malfunction: Procedure

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

   HINT: 

   First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.

3. Turn the ignition switch off.
4. Turn the ignition switch to ON, and wait for at least 60 seconds.
5. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1771 is not output.

   HINT: 

   Codes other than DTC B1771 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 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 front seat inner belt RH.

   OK

   Connectors are properly connected.

NG → CONNECT CONNECTOR 

OK: Go to next step 

1. Disconnect the connectors from the occupant classification ECU and front seat inner belt RH.
2. Check that the connectors (on the occupant classification ECU side and front passenger side buckle switch side) are not damaged. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

   OK

   Connectors are not deformed or damaged.

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
   Fig 1: Identifying Front Seat Wire RH

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   a9-9 (BSW) - Body ground	Ignition switch ON	Below 1 V
   a9-5 (BGND) - Body ground

3. Turn the ignition switch off.
4. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
5. Using a service wire, connect terminals 2 (RBE+) and 1 (RBE-) of connector C.
   NOTE:

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   a9-9 (BSW) - a9-5 (BGND)	Always	Below 1 Ω

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   a9-9 (BSW) - Body ground	Always	1 MΩ or higher
   a9-5 (BGND) - Body ground
   a9-9 (BSW) - a9-5 (BGND)

   TEXT IN ILLUSTRATION
   
   

   *1	Front Seat Wire RH
   *2	Front Seat Inner Belt RH
   *3	Occupant Classification ECU
   *4	Service Wire
   *5	Connector C
   *6	Connector B
   *a	Front view of wire harness connector (to Front Seat Inner Belt RH)
   *b	Front view of wire harness connector (to Occupant Classification ECU)

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and front seat inner belt RH.
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 the DTCs stored in memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.

5. Turn the ignition switch off.
6. Turn the ignition switch to ON, and wait for at least 60 seconds.
7. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1771 is not output.

   HINT: 

   Codes other than DTC B1771 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 cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the front seat inner belt RH. 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.
5. Turn the ignition switch to ON, and wait for at least 60 seconds.
6. Clear the DTCs stored in memory. Refer to DTC CHECK / CLEAR .

   HINT: 

   First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.

7. Turn the ignition switch off.
8. Turn the ignition switch to ON, and wait for at least 60 seconds.
9. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1771 is not output.

   HINT: 

   Codes other than DTC B1771 may be output at this time, but they are not related to this check.

NG → See step   7 

OK → 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 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.
5. Turn the ignition switch to ON, and wait for at least 60 seconds.
6. Clear the DTCs stored in 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. Turn the ignition switch to ON, and wait for at least 60 seconds.
2. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

   OK

   "Zero Point Calibration is complete." is displayed.

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