Toyota Sienna Service Manual: Front Occupant Classification Sensor LH Circuit
Malfunction
DTC B1780 Front Occupant Classification Sensor LH Circuit
Malfunction
DESCRIPTION
The front occupant classification sensor LH circuit consists of the occupant
classification ECU and the
front occupant classification sensor LH.
DTC B1780 is recorded when a malfunction is detected in the front occupant
classification sensor LH
circuit.
DTC No. |
DTC Detecting Condition |
Trouble Area |
B1780 |
- 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 front occupant classification sensor LH circuit
for 2 seconds.
- Front occupant classification sensor LH malfunction
- Occupant classification ECU malfunction
|
- Front seat assembly RH (Front occupant
classification sensor LH)
- Occupant classification ECU
- Front seat wire RH
|
WIRING DIAGRAM

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 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
- Turn the ignition switch to the ON position.
- Clear the DTCs stored in the memory.
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 (35).
OK:
DTC B1780 is not output.
HINT:
Codes other than DTC B1780 may be output at this time,
but they are not related to this check.
USE SIMULATION METHOD TO CHECK

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 occupant
classification sensor LH.
OK:
The connectors are properly connected
CONNECT CONNECTOR, THEN GO TO
STEP
1

3 CHECK FRONT SEAT WIRE RH (SHORT TO B+)

- Disconnect the connectors from the occupant
classification ECU and the front occupant classification
sensor LH.
- Connect the negative (-) terminal cable to the battery.
- Turn the ignition switch to the ON position.
- Measure the voltage according to the value(s) in the
table below.
Standard voltage

REPAIR OR REPLACE FRONT SEAT
WIRE
RH

4 CHECK FRONT SEAT WIRE RH (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 O5-1 (SVC1) and O5-3
(SGD1), and connect O5-2 (SIG1) and O5-3 (SGD1) of
connector "C".
NOTICE:
Do not forcibly insert a service wire into the
terminals of the connector when connecting.
- Measure the resistance according to the value(s) in the
table below.
Standard resistance

REPAIR OR REPLACE FRONT SEAT
WIRE
RH

5 CHECK FRONT SEAT WIRE RH (SHORT)

- Disconnect the service wire from connector "C".
- Measure the resistance according to the value(s) in the
table below.
Standard resistance

REPAIR OR REPLACE FRONT SEAT
WIRE
RH

6 CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

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

REPAIR OR REPLACE FRONT SEAT
WIRE
RH

7 CHECK DTC
- Connect the connectors to the occupant classification
ECU and the front occupant classification sensor LH.
- Connect the negative (-) terminal cable to the battery.
- Turn the ignition switch to the ON position.
- Clear the DTCs stored in the memory.
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 (35).
OK:
DTC B1780 is not output.
HINT:
Codes other than DTC B1780 may be output at this time,
but they are not related to this check.
USE SIMULATION METHOD TO CHECK

8 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.
HINT:
Perform the inspection using parts from a normal vehicle
if possible.

9 PERFORM ZERO POINT CALIBRATION
- Connect the negative (-) terminal cable to the battery.
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position.
- Using the intelligent tester, perform "Zero point
calibration" (28).
OK:
"COMPLETED" is displayed.
Go to step 12

10 PERFORM SENSITIVITY CHECK
- Using the intelligent tester, perform "Sensitivity check"
(28).
Standard value:
27 to 33 kg (59.52 to 72.75 lb)
Go to step 12

11 CHECK DTC
- Turn the ignition switch to the ON position.
- Clear the DTCs stored in the memory.
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 (35).
OK:
DTC B1780 is not output.
HINT:
Codes other than DTC B1780 may be output at this time,
but they are not related to this check.
END

12 REPLACE FRONT SEAT 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 assembly RH.

13 PERFORM ZERO POINT CALIBRATION
- Connect the negative (-) terminal cable to the battery.
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position.
- Using the intelligent tester, perform "Zero point
calibration" (28).
OK:
"COMPLETED" is displayed.

14 PERFORM SENSITIVITY CHECK
- Using the intelligent tester, perform "Sensitivity check"
(28).
Standard value:
27 to 33 kg (59.52 to 72.75 lb)

END
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 assembly ...
DTC B1781 Front Occupant Classification Sensor RH Circuit
Malfunction
DESCRIPTION
The front occupant classification sensor RH circuit consists of the occupant
classification ECU and the
front oc ...
Other materials:
Cold Start Ignition Timing Performance
DTC P050B Cold Start Ignition Timing Performance
DESCRIPTION
This monitor will run when the engine is started at -10 to 50C (14 to 122F)
of the engine coolant
temperature. The DTC will set after the engine idling for 13 seconds (2 trip
detection logic).
The DTC is designed to monitor the i ...
TC and CG Terminal Circuit
DESCRIPTION
DTC output mode is set by connecting terminals 13 (TC) and 4 (CG) of the
DLC3. The DTCs are indicated
by blinks of the tire pressure warning light.
WIRING DIAGRAM
HINT:
When each warning light blinks continuously, a ground short in the wiring of
terminal TC of the DLC3 or an ...
Terminals of ECU
1. CENTER AIRBAG SENSOR ASSEMBLY (w/ Side
Airbag)
2. CENTER AIRBAG SENSOR ASSEMBLY (w/o Side
Airbag)
...