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:
Microphone Circuit between Microphone and Radio and Navigation
Assembly
DESCRIPTION
This circuit sends a microphone signal from the microphone to the radio and
navigation assembly.
It also supplies power from the radio and navigation assembly to the microphone.
WIRING DIAGRAM
INSPECTION PROCEDURE
1 INSPECT RADIO AND NAVIGATION ASSEMBLY
Measure the v ...
Problem symptoms table
POWER WINDOW CONTROL SYSTEM (W/ JAM PROTECTION)
Symptom
Suspected Area
AUTO UP/DOWN function does not operate
Power window regulator motor assembly (Driver side)
Wire harness
Power window regulator master switch assembly
Remote ...
Disassembly
1. Remove oil filler cap sub-assembly
(A) remove the oil filler cap sub-assembly and oil filler
gasket.
2. REMOVE SPARK PLUG
(a) Remove the spark plugs.
3. REMOVE OIL PAN DRAIN PLUG
(a) Remove the oil pan drain plug and oil pan drain plug
gasket.
4. REMOVE VENTILATION VALVE SUB-ASSEMBLY
...