Toyota Sequoia (2005). Manual - part 364

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DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

DI–1251

1445

DTC

B1771

Passenger Side Buckle Switch Circuit 
Malfunction

CIRCUIT 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 the DTC B1771 and B1795 are output simultaneously.

DTC No.

DTC Detecting Condition

Trouble Area

B1771

The occupant classification ECU receives a line short

circuit signal, an open circuit signal, a short circuit to

ground signal or a short circuit to B+ signal in the passen-

ger side buckle switch circuit for 2 seconds.

Passenger side buckle switch malfunction

Occupant classification ECU malfunction

Front seat inner belt RH

Occupant classification ECU

Seat wire No. 1

HINT:
When DTC B1650/32 is detected as a result of troubleshooting for the supplemental restraint system, check
the DTCs stored in the occupant classification ECU. When DTC B1771 is output, perform troubleshooting
for the DTC.

DIDH4–01

H23244

Occupant Classification ECU

O6

O6

R

B17
Buckle SW RH

L

1

2

9

5

BSW

BGND

DI–1252

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DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

1446

WIRING DIAGRAM

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DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

DI–1253

1447

INSPECTION PROCEDURE

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the passenger seat installa-
tion bolts to see the under surface of 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 only as necessary.

1

Check DTC.

CHECK:
(a)

Turn the ignition switch to the ON position.

(b)

Clear the DTCs stored in memory (see page 

DI–1147

).

HINT:
First clear DTCs stored in the occupant classification ECU and then in the airbag sensor assembly.
(c)

Turn the ignition switch to the LOCK position.

(d)

Turn the ignition switch to the ON position.

(e)

Using the hand–held tester, check the DTCs of the occupant classification ECU (see page 

DI–1147

).

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

From the results of the above inspection, the malfunctioning part can now be considered normal.
To make sure of this, use the simulation method to check (see page 

DI–1137

).

H43103

H43111

H23819

Occupant
Classification ECU

BGND

BSW

C

B

D

A

Front Seat
Inner Belt RH

O6

Seat Wire No. 1

DI–1254

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DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

1448

2

Check connection of connectors.

PREPARATION:
(a)

Turn the ignition switch to the LOCK position.

(b)

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

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

The connectors are connected securely.

NG

Connect connectors, then go to step 1.

OK

3

Check seat wire No. 1 (short to B+).

PREPARATION:
(a)

Disconnect the connectors from the occupant classifica-
tion ECU and the front seat inner belt RH.

(b)

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

CHECK:
(a)

Turn the ignition switch to the ON position.

(b)

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

OK:

Tester Connection

Condition

Specified Condition

O6–9 (BSW) – 

Body ground

Ignition switch ON

Below 1 V

O6–5 (BGND) – 

Body ground

Ignition switch ON

Below 1 V

NG

Repair or replace seat wire No. 1.

OK