DTC B1773: Belt Tension Sensor Circuit Malfunction; DTC B1776: Seat Belt Tension Sensor Power Source Circuit Malfunction: Procedure

1. Turn the power 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 power switch OFF.
5. Turn the power switch ON (IG).
6. Check for the DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1773 and B1776 are not output.

   HINT: 

   Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.

NG → See step   2 

OK → See step   9 

1. Turn the power 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 seat belt tension sensor.

   OK

   Connectors are properly connected.

NG → CONNECT CONNECTORS PROPERLY 

OK: Go to next step 

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

   OK

   Connectors are not deformed or damaged.

   HINT: 

   If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

Fig 1: Checking Front Seat Wire RH

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the negative (-) terminal cable to the battery.
2. Turn the power switch ON (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard voltage

   Tester Connection	Switch Condition	Specified Condition
   a17-8 (GBT) - Body ground	Power switch ON (IG)	Below 1 V
   a17-16 (BT) - Body ground
   a17-17 (VBT) - Body ground

4. Turn the power switch OFF.
5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
6. Using 2 service wires, connect terminals 1 (GBT) and 3 (BT), and connect terminals 1 (GBT) and 2 (VBT) of connector C.
   NOTE:

   Do not forcibly insert the service wires 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	Switch Condition	Specified Condition
   a17-16 (BT) - a17-8 (GBT)	Always	Below 1 Ω
   a17-17 (VBT) - a17-8 (GBT)

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

   Standard resistance

   Tester Connection	Switch Condition	Specified Condition
   a17-8 (GBT) - Body ground	Always	1 MΩ or higher
   a17-16 (BT) - Body ground
   a17-17 (VBT) - Body ground
   a17-16 (BT) - a17-8 (GBT)
   a17-17 (VBT) - a17-8 (GBT)

NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and the seat belt tension sensor.
2. Connect the negative (-) terminal cable to the battery.
3. Turn the power switch ON (IG).
4. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
5. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
6. Turn the power switch OFF.
7. Turn the power switch ON (IG).
8. Check for the DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1773 and B1776 are not output.

   HINT: 

   Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.

OK → See step   9 

NG: Go to next step 

1. Turn the power switch OFF.
2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
3. Replace the front seat outer belt. Refer to REMOVAL .

   HINT: 

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

4. Connect the negative (-) terminal cable to the battery.
5. Turn the power switch ON (IG).
6. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
7. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
8. Turn the power switch OFF.
9. Turn the power switch ON (IG).
10. Check for the DTCs. Refer to DTC CHECK / CLEAR .

    OK

    DTC B1773 and B1776 are not output.

    HINT: 

    Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.

NG → See step   7 

OK → END 

1. Connect the Techstream to the DLC3.
2. Turn the power switch ON (IG).
3. Using the Techstream, save the ECU data from the ECU which has been installed on the vehicle. Refer to REGISTRATION .
4. Turn the power switch OFF.
5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
6. Replace the occupant classification ECU. Refer to DISASSEMBLY .
7. Connect the negative (-) terminal cable to the battery.
8. Turn the power switch ON (IG).
9. Using the Techstream, load the previous ECU data stored into the new ECU. Refer to REGISTRATION .
10. Turn the power switch OFF.
11. Turn the power switch ON (IG).
12. Clear the DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

    HINT: 

    If DTC is not cleared at this time, past DTC will remain.

NEXT: Go to next step 

1. Perform the sensitivity check. Refer to INITIALIZATION .

NEXT → END