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

1. Turn the ignition switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Check that the connectors are properly connected to the 2 rear 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 2 rear 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 

1. Connect the cable to the negative (-) auxiliary battery terminal.
   Fig 1: Front Seat Wire RH (Short To B+) connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch to ON (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   Y2-1 (SVC3) - Body ground	Ignition switch ON (IG)	Below 1 V
   Y2-2 (SVC4) - Body ground	Ignition switch ON (IG)	Below 1 V

4. Turn the ignition switch off.
5. Disconnect the cable from the negative (-) auxiliary battery terminal.
   TEXT IN ILLUSTRATION
   
   

   *1	Rear Occupant Classification Sensor LH
   *2	Rear Occupant Classification Sensor RH
   *3	Occupant Detection ECU
   *4	Front Seat Wire RH
   *a	Front view of wire harness connector (to Occupant Detection ECU)

NG → See step   11 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 2: Front Seat Wire RH (Short To Ground) connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Y2-1 (SVC3) - Body ground	Always	1 MΩ or higher
   Y2-2 (SVC4) - Body ground	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Rear Occupant Classification Sensor LH
   *2	Rear Occupant Classification Sensor RH
   *3	Occupant Detection ECU
   *4	Front Seat Wire RH
   *a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 3: Front Seat Wire RH (Short) connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Y2-1 (SVC3) - Y2-2 (SVC4)	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Rear Occupant Classification Sensor LH
   *2	Rear Occupant Classification Sensor RH
   *3	Occupant Detection ECU
   *4	Front Seat Wire RH
   *a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the connectors to the occupant detection ECU and 2 rear occupant classification sensors.
2. Connect the cable to the negative (-) auxiliary battery terminal.
3. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR .
4. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off.
6. Turn the ignition switch to ON (IG).
7. Check for DTCs. Refer to DTC CHECK / CLEAR .

   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. Turn the ignition switch off.

NG → See step   6 

OK → See step   13 

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Replace the occupant detection ECU with a known good one. Refer to REMOVAL .

   HINT: 

   Perform the following inspection using known good parts from another vehicle if possible.

3. Connect the cable to the negative (-) auxiliary battery terminal.
4. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR .
5. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR .
6. Turn the ignition switch off.
7. Turn the ignition switch to ON (IG).
8. Check for DTCs. Refer to DTC CHECK / CLEAR .

   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.

9. Turn the ignition switch off.
10. Disconnect the cable from the negative (-) auxiliary battery terminal.
11. Return the occupant detection ECU that was installed for testing to its original location. Refer to REMOVAL .

NG → See step   9 

OK: Go to next step 

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Replace the occupant detection ECU with a new one. Refer to REMOVAL .
3. Connect the cable to the negative (-) auxiliary battery terminal.

NEXT: Go to next step 

1. Using the Techstream, perform Zero Point Calibration and Sensitivity Check. Refer to INITIALIZATION .

NEXT → END 

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Replace the separate type front seat cushion spring assembly. Refer to REMOVAL w/ Non-removable Headrest. Refer to REMOVAL w/ Removable Headrest).
3. Connect the cable to the negative (-) auxiliary battery terminal.

NEXT: Go to next step 

1. Using the Techstream, perform Zero Point Calibration and Sensitivity Check. Refer to INITIALIZATION .

NEXT → END 

1. Disconnect the cable from the negative (-) auxiliary battery terminal.
2. Replace the separate type front seat cushion spring assembly. Refer to REMOVAL w/ Non-removable Headrest. Refer to REMOVAL w/ Removable Headrest).
   NOTE:

   Replace the front seat wire RH at the same time.

   HINT: 

   When the front seat wire RH has a short to B+, the rear occupant classification sensors will be damaged. Therefore, replace the front seat wire RH and the separate type front seat cushion spring assembly, which includes the rear occupant classification sensors.

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

NEXT: Go to next step 

1. Using the Techstream, perform Zero Point Calibration and Sensitivity Check. Refer to INITIALIZATION .

NEXT → END