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05-1086
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM 05IWZ-04
DTC B1793 OCCUPANT CLASSIFICATION SENSOR
POWER SUPPLY CIRCUIT MALFUNCTION
CIRCUIT 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
S The occupant classification ECU receives a line short
circuit signal, an open circuit signal, a short circuit to
S Seat adjuster frame assy (Occupant classification sensors)
ground signal or a short circuit to B+ signal in the occu-
B1793 S Front seat wire RH
pant classification sensor power supply circuit for 2 se-
S Occupant classification ECU
conds.
S Occupant classification ECU malfunction
HINT:
When DTC B1150/23 is detected as a result of troubleshooting for the supplemental restraint system, per-
form troubleshooting for DTC B1793 of the occupant classification system.
WIRING DIAGRAM
O8
Occupant Classification
Sensor Rear RH Occupant Classification ECU
6
Y
O4 SVC4
1
O6
Occupant Classification
Sensor Front RH
12
P
O4 SVC2
1
O7
Occupant Classification
Sensor Rear LH
5
Y-B
O4 SVC3
1
O5
Occupant Classification
Sensor Front LH
11
V
O4 SVC1
1
H43061
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1269
05-1087
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
INSPECTION PROCEDURE
HINT:
S If troubleshooting (wire harness inspection) is difficult to perform, remove the front RH seat assy instal-
lation bolts to see the under surface of seat cushion.
S 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
(a) Turn the ignition switch to the ON position.
(b) Clear the DTCs stored in memory (see page 05-777 ).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the airbag sensor assy center.
(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 (see page 05-777 ).
OK:
DTC B1793 is not output.
HINT:
Codes other than code B1793 may be output at this time, but they are not related to this check.
NG Go to step 2
OK
USE SIMULATION METHOD TO CHECK (SEE PAGE 05-770 )
2 CHECK CONNECTION OF CONNECTORS
(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.
(c) Check that the connectors are properly connected to the occupant classification ECU and the occu-
pant classification sensors.
OK:
The connectors are connected.
NG CONNECT CONNECTORS, THEN GO TO STEP
1
OK
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1270
05-1088
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
3 CHECK FRONT SEAT WIRE RH(TO B+)
(a) Disconnect the occupant classification ECU connector
O4 SVC3 and the 4 occupant classification sensor connectors.
(b) Connect the negative (-) terminal cable to the battery.
SVC4 (c) Turn the ignition switch to the ON position.
(d) Measure the voltage according to the value(s) in the table
SVC2
below.
Standard:
SVC1 Tester connection Condition Specified condition
H43111 O4-5 (SVC3) -
Ignition switch ON Below 1 V
Body ground
O4-6 (SVC4) -
Ignition switch ON Below 1 V
Body ground
O4-1 1 (SVC1) -
Ignition switch ON Below 1 V
Body ground
O4-12 (SVC2) -
Ignition switch ON Below 1 V
Body ground
NG REPAIR OR REPLACE FRONT SEAT WIRE RH
OK
4 CHECK FRONT SEAT WIRE RH(TO GROUND)
(a) Turn the ignition switch to the LOCK position.
O4 SVC3 (b) Disconnect the negative (-) terminal cable from the bat-
tery, and wait for at least 90 seconds.
SVC4 (c) Measure the resistance according to the value(s) in the
table below.
SVC2
Standard:
Tester connection Condition Specified condition
SVC1 O4-5 (SVC3) -
Always 1 M or Higher
H43111
Body ground
O4-6 (SVC4) -
Always 1 M or Higher
Body ground
O4-1 1 (SVC1) -
Always 1 M or Higher
Body ground
O4-12 (SVC2) -
Always 1 M or Higher
Body ground
NG REPAIR OR REPLACE FRONT SEAT WIRE RH
OK
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1271
05-1089
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
5 CHECK FRONT SEAT WIRE RH(OPEN)
(a) Measure the resistance according to the value(s) in the
O4 SVC3 table below.
Standard:
SVC4 Tester connection Condition Specified condition
O4-5 (SVC3) -
SVC2 Always Below 1
O7-1 (SVC3)
O4-6 (SVC4) -
Always Below 1
SVC1 O8-1 (SVC4)
O4-1 1 (SVC1) -
H43111 Always Below 1
O5-1 (SVC1)
O4-12 (SVC2) -
Always Below 1
O6-1 (SVC2)
NG REPAIR OR REPLACE FRONT SEAT WIRE RH
OK
6 CHECK FRONT SEAT WIRE RH(SHORT)
(a) Measure the resistance according to the value(s) in the
O4 SVC3 table below.
Standard:
SVC4 Tester connection Condition Specified condition
O4-5 (SVC3) -
SVC2 O4-6 (SVC4)
Always 1 M or Higher
O4-6 (SVC4) -
Always 1 M or Higher
SVC1 O4-1 1 (SVC1)
O4-1 1 (SVC1) -
H43111 Always 1 M or Higher
O4-12 (SVC2)
O4-12 (SVC2) -
Always 1 M or Higher
O4-5 (SVC3)
O4-12 (SVC2) -
Always 1 M or Higher
O4-6 (SVC4)
O4-1 1 (SVC1) -
Always 1 M or Higher
O4-5 (SVC3)
NG REPAIR OR REPLACE FRONT SEAT WIRE RH
OK
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1272
05-1090
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
7 RECHECK DTC
(a) Connect the occupant classification ECU connector and the 4 occupant classification sensor connec-
tors.
(b) Connect the negative (-) terminal cable to the battery.
(c) Turn the ignition switch to the ON position.
(d) Clear the DTCs stored in memory (see page 05-777 ).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the airbag sensor assy center.
(e) Turn the ignition switch to the LOCK position.
(f) Turn the ignition switch to the ON position.
(g) Using the hand-held tester, check the DTCs (see page 05-777 ).
OK:
DTC B1793 is not output.
HINT:
Codes other than code B1793 may be output at this time, but they are not related to this check.
NG Go to step 8
OK
USE SIMULATION METHOD TO CHECK (SEE PAGE 05-770 )
8 REPLACE OCCUPANT CLASSIFICATION ECU
(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.
(c) Replace the occupant classification ECU (see page 60-67 ).
HINT:
Perform the inspection using parts from a normal vehicle if possible.
NEXT
9 PERFORM ZERO POINT CALIBRATION
(a) Connect the negative (-) terminal cable to the battery.
(b) Connect the hand-held tester to the DLC3.
(c) Turn the ignition switch to the ON position.
(d) Using the hand-held tester, perform "Zero point calibration" (see page 05-767 ).
OK:
The "COMPLETED" is displayed.
NG Go to step 12
OK
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1273
05-1091
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
10 PERFORM SENSITIVITY CHECK
(a) Using the hand-held tester, perform "Sensitivity check" (see page 05-767 ).
Standard value: 27 to 33 kg (59.52 to 72.75 lb)
NG Go to step 12
OK
11 RECHECK DTC
(a) Turn the ignition switch to the ON position.
(b) Clear the DTCs stored in memory (see page 05-777 ).
HINT:
First clear DTCs stored in the occupant classification ECU and then in the airbag sensor assy center.
(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 (see page 05-777 ).
OK:
DTC B1793 is not output.
HINT:
Codes other than code B1793 may be output at this time, but they are related to this check.
NG Go to step 12
OK
END
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1274
05-1092
DIAGNOSTICS - SUPPLEMENTAL RESTRAINT SYSTEM
12 REPLACE SEAT ADJUSTER FRAME ASSY
(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.
(c) Replace the seat adjuster frame assy (see page 72-30 ).
NEXT
13 CHECK PERFORM ZERO POINT CALIBRATION
(a) Connect the negative (-) terminal cable to the battery.
(b) Connect the hand-held tester to the DLC3.
(c) Turn the ignition switch to the ON position.
(d) Using the hand-held tester, perform "Zero point calibration" (see page 05-767 ).
OK:
The "COMPLETED" is displayed.
NEXT
14 CHECK PERFORM SENSITIVITY CHECK
(a) Using the hand-held tester, perform "Sensitivity check" (see page 05-767 ).
Standard value: 27 to 33 kg (59.52 to 72.75 lb)
NEXT
END
2005 SIENNA REPAIR MANUAL (RM1163U)
Author : Date : 1275
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