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.
DTC No. |
DTC Detecting Condition |
Trouble Area |
B1793 |
- 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 occupant classification sensor power supply
circuit for 2 seconds.
- Occupant classification ECU malfunction
|
- Front seat assembly RH (Occupant classification
sensors)
- 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 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 (35).
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" (28).
OK:
"COMPLETED" is displayed
10 PERFORM SENSITIVITY CHECK
- Using the intelligent tester, perform "Sensitivity check"
(28).
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 (35).
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" (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 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:
If the shift lever cannot
be shifted from P
If the shift lever cannot be shifted with your foot on the brake
pedal, there may be a problem with the shift lock system (a system
to prevent accidental operation of the shift lever). Have the
vehicle inspected by your Toyota dealer immediately.
The following steps may be used as an emergency ...
Inspection
1. INSPECT BRAKE VACUUM CHECK VALVE ASSEMBLY
(a) Check the vacuum check valve.
(1) Slide the clip and disconnect the vacuum hose.
(2) Remove the vacuum check valve.
(3) Check that there is ventilation from the booster
to the engine, and no ventilation from the
engine to the booster.
...
Rear wheel alignment
ADJUSTMENT
NOTICE:
For vehicles equipped with VSC, if wheel alignment has
been adjusted, and if suspension or underbody
components have been removed/installed or replaced, be
sure to perform the following initialization procedure in
order for the system to function normally:
1. Disconnect the ...