DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction [08/2015 - 08/2019]: Procedure

CHECK FOR DTC
1. Turn the engine switch on (IG), and wait for at least 60 seconds.
2. Clear the DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  HINT:
  - First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
  - Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
3. Turn the engine switch off.
4. Turn the engine switch on (IG), and wait for at least 60 seconds.
5. Check for DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  OK
  
  DTC B1793 is not output.
  
  HINT:
  
  DTCs other than DTC B1793 may be output at this time, but they are not related to this check.
Result:

OK

USE SIMULATION METHOD TO CHECK

(Refer to DIAGNOSIS SYSTEM [08/2015 - ] )

Result:

NG

See step 2
CHECK CONNECTION OF CONNECTOR
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Check that the connectors are properly connected to the occupant classification ECU and occupant classification sensors.
  OK
  
  Connectors are properly connected.
Result:

NG

CONNECT CONNECTOR

Result:

OK

See step 3
CHECK CONNECTOR
1. Disconnect the connectors from the occupant classification ECU and 4 occupant classification sensors.
2. Check that the connectors (on the occupant classification ECU side and occupant classification sensor side) are not damaged (Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [08/2015 - ] ).
  OK
  
  Connectors are not deformed or damaged.
Result:

NG

REPLACE FRONT SEAT WIRE RH

(Refer to DISASSEMBLY [08/2015 - 08/2021] )

Result:

OK

See step 4

CHECK FRONT SEAT WIRE RH (OCCUPANT CLASSIFICATION SENSOR - OCCUPANT CLASSIFICATION ECU)

Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TEXT IN ILLUSTRATION

*1	Front Seat Wire RH	*2	Occupant Classification Sensor
*3	Occupant Classification ECU	*4	Connector B
*5	Connector C	-	-
*a	Front view of wire harness connector (to Occupant Classification ECU)	*b	Front view of wire harness connector (to Front Occupant Classification Sensor LH)
*c	Front view of wire harness connector (to Front Occupant Classification Sensor RH)	*d	Front view of wire harness connector (to Rear Occupant Classification Sensor LH)
*e	Front view of wire harness connector (to Rear Occupant Classification Sensor RH)	-	-

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
a3-11 (SVC1) - Body ground	Engine switch on (IG)	Below 1 V
a3-12 (SVC2) - Body ground
a3-5 (SVC3) - Body ground
a3-6 (SVC4) - Body ground

Turn the engine switch off.
Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
a3-11 (SVC1) - a6-1 (SVC1)	Always	Below 1 Ω
a3-12 (SVC2) - a2-1 (SVC2)
a3-5 (SVC3) - a7-1 (SVC3)
a3-6 (SVC4) - a1-1 (SVC4)
a3-11 (SVC1) - a3-12 (SVC2)	Always	1 MΩ or higher
a3-11 (SVC1) - a3-5 (SVC3)
a3-11 (SVC1) - a3-6 (SVC4)
a3-12 (SVC2) - a3-5 (SVC3)
a3-12 (SVC2) - a3-6 (SVC4)
a3-5 (SVC3) - a3-6 (SVC4)
a3-11 (SVC1) - Body ground
a3-12 (SVC2) - Body ground
a3-5 (SVC3) - Body ground
a3-6 (SVC4) - Body ground

Result:

REPLACE FRONT SEAT WIRE RH

(Refer to DISASSEMBLY [08/2015 - 08/2021] )

Result:

See step 5

CHECK FOR DTC
1. Connect the connectors to occupant classification ECU and 4 occupant classification sensors.
2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Clear the DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  HINT:
  - First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
  - Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
5. Turn the engine switch off.
6. Turn the engine switch on (IG), and wait for at least 60 seconds.
7. Check for DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  OK
  
  DTC B1793 is not output.
  
  HINT:
  
  DTCs other than DTC B1793 may be output at this time, but they are not related to this check.
Result:

OK

USE SIMULATION METHOD TO CHECK

(Refer to DIAGNOSIS SYSTEM [08/2015 - ] )

Result:

NG

See step 6
REPLACE OCCUPANT CLASSIFICATION ECU
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the occupant classification ECU (Refer to REMOVAL [08/2015 - ] ).
  HINT:
  
  Perform the inspection using parts from a normal vehicle when possible.
Result:

NEXT

See step 7
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Turn the engine switch on (IG).
3. Perform the zero point calibration (Refer to INITIALIZATION [08/2015 - ] ).
  OK
  
  "Zero Point Calibration is complete." is displayed.
Result:

NG

See step 10

Result:

OK

See step 8
PERFORM SENSITIVITY CHECK
1. Perform the sensitivity check (Refer to INITIALIZATION [08/2015 - ] ).
  Standard
  
  27 to 33 kg (59.5 to 72.8 lb)
Result:

NG

See step 10

Result:

OK

See step 9
CHECK FOR DTC
1. Clear the DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  HINT:
  - First clear the DTCs stored in the occupant classification ECU, and then clear the DTCs stored in the center airbag sensor.
  - Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
2. Turn the engine switch off.
3. Turn the engine switch on (IG), and wait for at least 60 seconds.
4. Check for DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] ).
  OK
  
  DTC B1793 is not output.
  
  HINT:
  
  DTCs other than DTC B1793 may be output at this time, but they are not related to this check.
Result:

OK

END (OCCUPANT CLASSIFICATION ECU IS DEFECTIVE)

Result:

NG

See step 10
REPLACE SEPARATE TYPE FRONT SEAT CUSHION SPRING ASSEMBLY RH
1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. Replace the separate type front seat cushion spring RH (Refer to DISASSEMBLY [08/2015 - 08/2021] ).
  HINT:
  
  Perform the inspection using parts from a normal vehicle when possible.
Result:

NEXT

See step 11
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
2. Turn the engine switch on (IG).
3. Perform the zero point calibration (Refer to INITIALIZATION [08/2015 - ] ).
  OK
  
  "Zero Point Calibration is complete." is displayed.
Result:

NEXT

See step 12
PERFORM SENSITIVITY CHECK
1. Perform the sensitivity check (Refer to INITIALIZATION [08/2015 - ] ).
  Standard
  
  27 to 33 kg (59.5 to 72.8 lb)
Result:

NEXT

END (SEPARATE TYPE FRONT SEAT CUSHION SPRING RH IS DEFECTIVE)