Toyota Sienna Service Manual: Occupant Classification Sensor Power Supply
Circuit Malfunction
DTC B1793 Occupant Classification Sensor Power Supply
Circuit Malfunction
DESCRIPTION
The occupant classification sensor power supply circuit consists of the
occupant classification ECU and
the occupant classification sensors.
DTC B1793 is recorded when a malfunction is detected in the occupant
classification sensor power
supply circuit

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.
OK:
DTC B1793 is not output.
HINT:
Codes other than DTC B1793 may be output at this time,
but they are not related to this 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 occupant
classification sensors.
OK:
The connectors are properly connected.
3 CHECK FRONT SEAT WIRE RH (SHORT TO B+)

- Disconnect the connectors from the occupant
classification ECU and the 4 occupant classification
sensors.
- 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

4 CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

- Turn the ignition switch to the LOCK position.
- Disconnect the negative (-) terminal cable from the
battery, and wait for at least 90 seconds.
- Measure the resistance according to the value(s) in the
table below.
Standard resistance

5 CHECK FRONT SEAT WIRE RH (OPEN)

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

6 CHECK FRONT SEAT WIRE RH (SHORT)

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

7 CHECK DTC
- Connect the connectors to the occupant classification
ECU and the 4 occupant classification sensors.
- 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.
OK:
DTC B1793 is not output.
HINT:
Codes other than DTC B1793 may be output at this time,
but they are not related to this 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".
OK:
"COMPLETED" is displayed.
10 PERFORM SENSITIVITY CHECK
- Using the intelligent tester, perform "Sensitivity check".
Standard value:
27 to 33 kg (59.52 to 72.75 lb)
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.
OK:
DTC B1793 is not output.
HINT:
Codes other than DTC B1793 may be output at this time,
but they are related to this check.
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 (
for flat type, SE-48 for manual seat, SE-58 for power
seat).
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".
OK:
"COMPLETED" is displayed.
14 PERFORM SENSITIVITY CHECK
- Using the intelligent tester, perform "Sensitivity check".
Standard value:
27 to 33 kg (59.52 to 72.75 lb)
END
DTC B1790 Center Airbag Sensor Assembly Communication
Circuit Malfunction
DESCRIPTION
The center airbag sensor assembly communication circuit consists of the
occupant classification ECU and
the ...
DTC B1794 Open in Occupant Classification ECU Battery
Positive Line
DESCRIPTION
This circuit consists of the occupant classification ECU and the power source
circuit (battery, fuse, wire
harness ...
Other materials:
Throttle Actuator Control Motor Current Range / Performance
DESCRIPTION
The ETCS (Electronic Throttle Control System) has a dedicated power supply
circuit. The voltage (+BM)
is monitored and when it is low (less than 4 V), the ECM determines that there
is a malfunction in the
ETCS and cuts off the current to the throttle actuator.
When the volt ...
High mounted stop light assembly
COMPONENTS
REMOVAL
1. REMOVE BACK DOOR GARNISH CENTER (w/ Rear Spoiler)
2. REMOVE REAR SPOILER COVER (w/ Rear Spoiler)
3. REMOVE CENTER STOP LIGHT ASSEMBLY
w/o Rear spoiler:
Disconnect the connector and remove the 2
screws and the center stop light assembly.
...
Removal
1. REMOVE FRONT DOOR WINDOW FRAME MOULDING
Remove the screw.
Using a heat light, heat the front door window frame
moulding between 40 to 60 C (104 to 140 F).
NOTICE:
Do not heat the front door window frame
moulding excessively.
Slide the front door window frame moulding upward
...