DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction: Procedure

CHECK CONNECTORS
1. Turn the power switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Check that the connectors are properly connected to the 4 occupant classification sensors and occupant detection ECU.
  OK
  
  The connectors are properly connected.
  
  HINT:
  
  If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.
4. Disconnect the connectors from the 4 occupant classification sensors and occupant detection ECU.
5. Check that the terminals of the connectors are not damaged.
  OK
  
  The terminals are not deformed or damaged.
NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

Connect the cable to the negative (-) auxiliary battery terminal.

Fig 1: Identifying W3 Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Turn the power switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
W3-5 (SVC3) - Body ground	Power switch on (IG)	Below 1 V
W3-6 (SVC4) - Body ground	Power switch on (IG)	Below 1 V
W3-11 (SVC1) - Body ground	Power switch on (IG)	Below 1 V
W3-12 (SVC2) - Body ground	Power switch on (IG)	Below 1 V

TEXT IN ILLUSTRATION

*1	4 Occupant Classification Sensors
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

Turn the power switch off.

Fig 2: Identifying W3 Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the cable from the negative (-) auxiliary battery terminal.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
W3-5 (SVC3) - Body ground	Always	1 MΩ or higher
W3-6 (SVC4) - Body ground	Always	1 MΩ or higher
W3-11 (SVC1) - Body ground	Always	1 MΩ or higher
W3-12 (SVC2) - Body ground	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

*1	4 Occupant Classification Sensors
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (OPEN)

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

Fig 3: Identifying W3, W6, W1, W2, And W7 Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
W3-5 (SVC3) - W7-1 (SVC3)	Always	Below 1 Ω
W3-6 (SVC4) - W1-1 (SVC4)	Always	Below 1 Ω
W3-11 (SVC1) - W6-1 (SVC1)	Always	Below 1 Ω
W3-12 (SVC2) - W2-1 (SVC2)	Always	Below 1 Ω

TEXT IN ILLUSTRATION

*1	4 Occupant Classification Sensors	*2	Occupant Detection ECU
*3	Front Seat Wire RH	*4	Connector B
*5	Connector C	*6	Front Occupant Classification Sensor LH
*7	Rear Occupant Classification Sensor RH	*8	Front Occupant Classification Sensor RH
*9	Rear Occupant Classification Sensor LH	-	-
*a	Front view of wire harness connector (to Occupant Detection ECU)	*b	Front view of wire harness connector (to 4 Occupant Classification Sensors)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT)

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

Fig 4: Identifying W3 Connector Terminals

Standard Resistance

Tester Connection	Condition	Specified Condition
W3-5 (SVC3) - W3-6 (SVC4)	Always	1 MΩ or higher
W3-5 (SVC3) - W3-11 (SVC1)	Always	1 MΩ or higher
W3-5 (SVC3) - W3-12 (SVC2)	Always	1 MΩ or higher
W3-6 (SVC4) - W3-11 (SVC1)	Always	1 MΩ or higher
W3-6 (SVC4) - W3-12 (SVC2)	Always	1 MΩ or higher
W3-11 (SVC1) - W3-12 (SVC2)	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

*1	4 Occupant Classification Sensors
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK DTC
1. Connect the connectors to the occupant detection ECU and 4 occupant classification sensors.
2. Connect the cable to the negative (-) auxiliary battery terminal.
3. Turn the power switch on (IG).
4. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR [08/2012 - ] .
5. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR [08/2012 - ] .
6. Turn the power switch off.
7. Turn the power switch on (IG).
8. Check for DTCs. Refer to DTC CHECK / CLEAR [08/2012 - ] .
  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.
NG → See step 7

OK → See step 10
REPLACE FRONT SEAT CUSHION SPRING ASSEMBLY
1. Turn the power switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Replace the front seat cushion spring assembly. Refer to DISASSEMBLY [08/2012 - ] for Manual seat. Refer to DISASSEMBLY [08/2012 - ] for Power seat).
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) auxiliary battery terminal.
2. Turn the power switch on (IG).
3. Using the Techstream, perform Zero Point Calibration. Refer to INITIALIZATION [08/2012 - ] .
NEXT: Go to next step
PERFORM SENSITIVITY CHECK
1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION [08/2012 - ] .
NEXT → END
USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2012 - ]