Supplemental Restraint Systems. Dtc B1771 Passenger Side Buckle Switch Circuit Malfunction

The passenger side buckle switch circuit consists of the occupant classification ECU and the front seat inner belt assembly RH.
DTC B1771 is recorded when a malfunction is detected in the passenger side buckle switch circuit.
Troubleshoot DTC B1771 first when DTCs B1771 and B1795 are output simultaneously.

DTC No.	DTC Detecting Condition	Trouble Area
B1771	Occupant classification ECU detects line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in passenger side buckle switch circuit for 2 seconds Passenger side buckle switch malfunction Occupant classification ECU malfunction	Floor wire Front seat inner belt assembly RH (Buckle switch RH) Occupant classification ECU

WIRING DIAGRAM

Yaris. Ncp93, 131.Supplemental Restraint Systems.Airbag System (For Sedan).
Dtc
B1771 Passenger Side Buckle Switch Circuit Malfunction

INSPECTION PROCEDURE

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of the seat cushion.
In the above case, hold the seat so that it does not tip over. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.

1.CHECK DTC

Turn the ignition switch to the on position.

Clear the DTCs stored in the memory (YARIS_NCP93 RM0000010VK06DX.html).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

Turn the ignition switch to the lock position.

Turn the ignition switch to the on position.

Check the DTCs (YARIS_NCP93 RM0000010VK06DX.html).
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.

USE SIMULATION METHOD TO CHECK

NG

2.CHECK CONNECTION OF CONNECTORS

Turn the ignition switch to the lock position.

Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

Check that the connectors are properly connected to the occupant classification ECU and the front seat inner belt assembly RH.
OK:
The connectors are properly connected.

CONNECT CONNECTORS

OK

3.CHECK FLOOR WIRE (TO B+)

Disconnect the connectors from the occupant classification ECU and the front seat inner belt assembly RH.

Connect the negative (-) terminal cable to the battery.

Turn the ignition switch to the on position.

Measure the voltage.
Standard voltage:
Tester connection
Condition
Specified condition
J24-9 (BSW) -
Body ground
Ignition switch on
Below 1 V
J24-5 (BGND) -
Body ground
Ignition switch on
Below 1 V

REPAIR OR REPLACE FLOOR WIRE

OK

4.CHECK FLOOR WIRE (FOR OPEN)

Turn the ignition switch to the lock position.

Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

Using a service wire, connect J11-2 and J11-1 of connector C.
NOTICE:
Do not forcibly insert the service wire into the terminals of the connector when connecting.

Measure the resistance.
Standard resistance:
Tester connection
Condition
Specified condition
J24-9 (BSW) -
J24-5 (BGND)
Always
Below 1 Ω

REPAIR OR REPLACE FLOOR WIRE

OK

5.CHECK FLOOR WIRE (FOR SHORT)

Disconnect the service wire from connector C.

Measure the resistance.
Standard resistance:
Tester connection
Condition
Specified condition
J24-9 (BSW) -
J24-5 (BGND)
Always
1 MΩ or higher

REPAIR OR REPLACE FLOOR WIRE

OK

6.CHECK FLOOR WIRE (TO GROUND)

Measure the resistance.
Standard resistance:
Tester connection
Condition
Specified condition
J24-9 (BSW) -
Body ground
Always
1 MΩ or higher
J24-5 (BGND) -
Body ground
Always
1 MΩ or higher

REPAIR OR REPLACE FLOOR WIRE

OK

7.CHECK DTC

Connect the connectors to the occupant classification ECU and the front seat inner belt assembly RH.

Connect the negative (-) terminal cable to the battery.

Turn the ignition switch to the on position.

Clear the DTCs stored in the memory (YARIS_NCP93 RM0000010VK06DX.html).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

Turn the ignition switch to the lock position.

Turn the ignition switch to the on position.

Check the DTCs (YARIS_NCP93 RM0000010VK06DX.html).
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.

USE SIMULATION METHOD TO CHECK

NG

8.REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

Turn the ignition switch to the lock position.

Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

Replace the front seat inner belt assembly RH (YARIS_NCP93 RM000002AQ700CX.html ).
HINT:
Perform the inspection using parts from a normal vehicle if possible.

Connect the negative (-) terminal cable to the battery.

Turn the ignition switch to the on position.

Clear the DTCs stored in the memory (YARIS_NCP93 RM0000010VK06DX.html).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

Turn the ignition switch to the lock position.

Turn the ignition switch to the on position.

Check the DTCs (YARIS_NCP93 RM0000010VK06DX.html).
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.

END

NG

9.REPLACE OCCUPANT CLASSIFICATION ECU

Turn the ignition switch to the lock position.

Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

Replace the occupant classification ECU (YARIS_NCP93 RM0000012DU00KX.html).

NEXT

10.PERFORM ZERO POINT CALIBRATION

Connect the negative (-) terminal cable to the battery.

Connect the Techstream to the DLC3.

Turn the ignition switch to the on position.

Using the Techstream, perform the zero point calibration (YARIS_NCP93 RM0000010VN06EX.html).
OK:
COMPLETED is displayed on the tester.

NEXT

11.PERFORM SENSITIVITY CHECK

Using the Techstream, perform the sensitivity check (YARIS_NCP93 RM0000010VN06EX.html).
1. Confirm that nothing is placed on the passenger seat.
2. Confirm that the beginning sensor reading is within the standard range.
  Standard range:
  -3.2 to 3.2 kg (-7 to 7 lb)
3. Place a 30 kg (66.14 lb) weight (e.g. a lead mass) onto the front passenger seat.
4. Confirm that the sensitivity is within the standard range.
  Standard range:
  27 to 33 kg (59.52 to 72.75 lb)
  HINT:
  When performing the sensitivity check, use a solid metal weight (the check result may not be accurate if a liquid weight is used).

END

Tester connection	Condition	Specified condition
J24-9 (BSW) - Body ground	Ignition switch on	Below 1 V
J24-5 (BGND) - Body ground	Ignition switch on	Below 1 V