Toyota Tundra. Manual — part 2625

DTC B1771: PASSENGER SIDE BUCKLE SWITCH CIRCUIT MALFUNCTION

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 TROUBLE DETECTION CONDITION TABLE

ECU

B1788

Rear Occupant
Classification Sensor RH
Collision Detection



Front seat frame with
adjuster RH (Rear
occupant detection
sensor RH)



Occupant classification
ECU

ON

B1790

Center Airbag Sensor
Assembly
Communication Circuit
Malfunction



No. 2 floor wire



Front seat wire RH



Occupant classification
ECU



Center airbag sensor

ON

B1793

Occupant Classification
Sensor Power Supply
Circuit Malfunction



Front seat frame with
adjuster RH (Occupant
detection sensors)



Front seat wire RH



Occupant classification
ECU

ON

B1794

Open in Occupant
Classification ECU
Battery Positive Line



Harness and connector



Occupant classification
ECU

ON

B1795

Occupant Classification
ECU Malfunction

Occupant classification ECU

ON

B1796

Sleep Operation Failure
of Occupant
Classification ECU

Occupant classification ECU

ON

DTC

Code

DTC Detection Condition

Trouble Area

One of following conditions is met:



Occupant classification ECU detects line short circuit



Front seat wire



RH Front seat inner belt

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

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

Fig. 205: Identifying Passenger Side Buckle Switch Circuit Malfunction - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

INSPECTION PROCEDURE

B1771

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

RH (Passenger side
buckle switch)



Occupant classification
ECU

NOTE:

After the ignition switch is turned OFF, the navigation system requires
approximately 90 seconds to record various types of memory and settings. As a

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

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.

1. CHECK FOR DTC

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

b. Clear the DTCs stored in the memory (see DTC CHECK/CLEAR ).

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 ON, and wait for at least 60 seconds.

e. Check for DTCs (see 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: Go to step 2

OK: USE SIMULATION METHOD TO CHECK (See DIAGNOSIS SYSTEM )

2. CHECK CONNECTION OF CONNECTOR

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 CONNECTOR

OK: Go to next step

3. CHECK CONNECTOR

result, after turning the ignition switch OFF, wait 90 seconds or more before
disconnecting the cable from the negative (-) battery terminal.

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

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 ELECTRONIC CIRCUIT INSPECTION PROCEDURE ).

OK: Connectors are not deformed or damaged.

NG: REPLACE FRONT SEAT WIRE RH

OK: Go to next step

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 ON, and wait for at least 60 seconds.

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

Standard voltage:

for Power Seat

TESTER CONNECTION SPECIFIED CONDITION TABLE

for Manual Seat

TESTER CONNECTION SPECIFIED CONDITION TABLE

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.

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

Tester Connection

Switch Condition Specified Condition

Y2-9 (BSW) - Body ground

Ignition switch ON

Below 1 V

Y2-5 (BGND) - Body ground

Tester Connection

Switch Condition Specified Condition

Q11-9 (BSW) - Body ground

Ignition switch ON

Below 1 V

Q11-5 (BGND) - Body ground

NOTE:

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

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra