Toyota Tundra Service Manual: Passenger Side Buckle Switch Circuit Malfunction (B1771)

DESCRIPTION

The passenger side buckle switch circuit consists of the occupant classification ECU and the front seat inner belt 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 Code

DTC Detection Condition

Trouble Area

B1771

One of following conditions is met:

  • 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
  • Front seat wire RH
  • Front seat inner belt RH (Passenger side buckle switch)
  • Occupant classification ECU

HINT:

  • When DTC B1650/32 is detected as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1771 of the occupant classification system.
  • Use the Techstream to check for DTCs of the occupant classification ECU, otherwise the DTC cannot be read.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work (See page ).
  • When disconnecting the cable from the negative (-) battery terminal while performing repairs, some systems need to be initialized after the cable is reconnected (See page ).

HINT:

  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front seat RH installation bolts to see the undersurface of the seat cushion.
  • In the above case, hold the seat so that it does not fall down. 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.

PROCEDURE

1.

CHECK FOR DTC

(a) Turn the ignition switch to ON, and wait for at least 60 seconds.

(b) Clear the DTCs stored in the memory (see page ).

HINT:

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

(c) Turn the ignition switch off.

(d) Turn the ignition switch to ON, and wait for at least 60 seconds.

(e) Check for DTCs (see page ).

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.

OK

USE SIMULATION METHOD TO CHECK

NG

2.

CHECK CONNECTION OF CONNECTORS

(a) Turn the ignition switch off.

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

(c) Check that the connectors are properly connected to the occupant classification ECU and the front seat inner belt RH.

OK:

Connectors are properly connected.

NG

CONNECT CONNECTORS

OK

3.

CHECK CONNECTORS

(a) Disconnect the connectors from the occupant classification ECU and the front seat inner belt RH.

(b) Check that the connectors (on the occupant classification ECU side and passenger side buckle switch side) are not damaged (see page ).

OK:

Connectors are not deformed or damaged.

NG

REPLACE FRONT SEAT WIRE RH

OK

4.

CHECK FRONT SEAT WIRE RH

(a) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(b) Turn the ignition switch to ON, and wait for at least 60 seconds.

(c) Measure the voltage according to the value(s) in the table below.

Standard voltage:

Tester Connection

Switch Condition

Specified Condition

Y2-9 (BSW) - Body ground

Ignition switch ON

Below 1 V

Y2-5 (BGND) - Body ground

(d) Turn the ignition switch off.

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

(f) Using a service wire, connect terminals 1 (RBE+) and 2 (RBE-) of connector C.

NOTICE:

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

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

Standard resistance:

Tester Connection

Condition

Specified Condition

Y2-9 (BSW) - Y2-5 (BGND)

Always

Below 1 Ω

(h) Disconnect the service wire from connector C.

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

Standard resistance:

Tester Connection

Condition

Specified Condition

Y2-9 (BSW) - Body ground

Always

1 MΩ or higher

Y2-5 (BGND) - Body ground

Y2-9 (BSW) - Y2-5 (BGND)

NG

REPLACE FRONT SEAT WIRE RH

OK

5.

CHECK FOR DTC

(a) Connect the connectors to the occupant classification ECU and the front seat inner belt RH.

(b) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(c) Turn the ignition switch to ON, and wait for at least 60 seconds.

(d) Clear the DTCs stored in the memory (see page ).

HINT:

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

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 60 seconds.

(g) Check for DTCs (see page ).

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.

OK

USE SIMULATION METHOD TO CHECK

NG

6.

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

(a) Turn the ignition switch off.

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

(c) Replace the front seat inner belt RH (see page ).

HINT:

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

(d) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(e) Turn the ignition switch to ON, and wait for at least 60 seconds.

(f) Clear the DTCs stored in the memory (see page ).

HINT:

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

(g) Turn the ignition switch off.

(h) Turn the ignition switch to ON, and wait for at least 60 seconds.

(i) Check for DTCs (see page ).

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.

OK

END

NG

7.

REPLACE OCCUPANT CLASSIFICATION ECU

(a) Turn the ignition switch off.

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

(c) Replace the occupant classification ECU.

  • for Manual Seat (see page ).
  • for Power Seat (see page ).

HINT:

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

(d) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(e) Turn the ignition switch to ON, and wait for at least 60 seconds.

(f) Clear the DTCs stored in the memory (see page ).

HINT:

If the DTCs are not cleared at this time, past DTCs will remain.

NEXT

8.

PERFORM ZERO POINT CALIBRATION

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON, and wait for at least 60 seconds.

(c) Using the Techstream, perform the zero point calibration (see page ).

NEXT

9.

PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (see page ).

Standard range:

27 to 33 kg (59.5 to 72.8 lb)

NEXT

END

    Occupant Classification System

    Front Occupant Classification Sensor LH Circuit Malfunction (B1780)

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