Toyota Venza: Occupant Classification Sensor Power Supply Circuit Malfunction (B1793)

Toyota Venza Service Manual / Supplemental Restraint Systems / Occupant Classification System / Occupant Classification Sensor Power Supply Circuit Malfunction (B1793)

DESCRIPTION

The occupant classification sensor power supply circuit consists of the occupant classification ECU and occupant classification sensors.

DTC B1793 is recorded when a malfunction is detected in the occupant classification sensor power supply circuit.

DTC No.	DTC Detection Condition	Trouble Area
B1793	The occupant classification ECU receives a line short circuit signal, an open circuit signal, a short circuit to ground signal or a short circuit to B+ signal in the occupant classification sensor power supply circuit for 2 seconds. Occupant classification ECU malfunction	Front seat frame with adjuster assembly RH (Occupant classification sensors) Occupant classification ECU Front seat wire RH

HINT:

When DTC B1650/32 is detected as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant classification ECU. When DTC B1793 is output, perform troubleshooting for the DTC.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see under the seat cushion.
In the above case, hold the seat so that it does not fall down. Hold the seat only as necessary because holding the seat for a long period of time may cause seat rail deformation.

PROCEDURE

1.	CHECK CONNECTORS

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

(c) Check that the connectors are properly connected to the 4 occupant classification sensors and occupant classification ECU.

OK:

The connectors are properly connected.

HINT:

If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the 4 occupant classification sensors and occupant classification ECU.

(e) Check that the terminals of connectors are not damaged.

OK:

The terminals are not deformed or damaged.

REPLACE FRONT SEAT WIRE RH

2.	CHECK FRONT SEAT WIRE RH (SHORT TO B+)

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

(b) Turn the ignition switch to ON.

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
S13-5 (SVC3) - Body ground	Ignition switch ON	Below 1 V
S13-6 (SVC4) - Body ground	Ignition switch ON	Below 1 V
S13-11 (SVC1) - Body ground	Ignition switch ON	Below 1 V
S13-12 (SVC2) - Body ground	Ignition switch ON	Below 1 V

Text in Illustration

*1	Front view of wire harness connector (to Occupant Classification ECU)

REPLACE FRONT SEAT WIRE RH

3.	CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

Standard Resistance:

Tester Connection	Condition	Specified Condition
S13-5 (SVC3) - Body ground	Always	1 MΩ or higher
S13-6 (SVC4) - Body ground	Always	1 MΩ or higher
S13-11 (SVC1) - Body ground	Always	1 MΩ or higher
S13-12 (SVC2) - Body ground	Always	1 MΩ or higher

Text in Illustration

*1	Front view of wire harness connector (to Occupant Classification ECU)

REPLACE FRONT SEAT WIRE RH

4.	CHECK FRONT SEAT WIRE RH (OPEN)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S13-5 (SVC3) - S5-1 (SVC3)	Always	Below 1 Ω
S13-6 (SVC4) - S6-1 (SVC4)	Always	Below 1 Ω
S13-11 (SVC1) - S3-1 (SVC1)	Always	Below 1 Ω
S13-12 (SVC2) - S4-1 (SVC2)	Always	Below 1 Ω

Text in Illustration

*1	Front LH
*2	Front RH
*3	Rear LH
*4	Rear RH
*5	Front view of wire harness connector (to Occupant Classification Sensor)
*6	Front view of wire harness connector (to Occupant Classification ECU)

REPLACE FRONT SEAT WIRE RH

5.	CHECK FRONT SEAT WIRE RH (SHORT)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S13-5 (SVC3) - S13-6 (SVC4)	Always	1 MΩ or higher
S13-5 (SVC3) - S13-11 (SVC1)	Always	1 MΩ or higher
S13-5 (SVC3) - S13-12 (SVC2)	Always	1 MΩ or higher
S13-6 (SVC4) - S13-11 (SVC1)	Always	1 MΩ or higher
S13-6 (SVC4) - S13-12 (SVC2)	Always	1 MΩ or higher
S13-11 (SVC1) - S13-12 (SVC2)	Always	1 MΩ or higher

Text in Illustration

*1	Front view of wire harness connector (to Occupant Classification ECU)

REPLACE FRONT SEAT WIRE RH

CHECK DTC

(a) Connect the connectors to the occupant classification ECU and the 4 occupant classification sensors.

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

(d) Clear the DTCs stored in the occupant classification ECU (See page ).

(e) Clear the DTCs stored in the center airbag sensor assembly (See page ).

(f) Turn the ignition switch off.

(g) Turn the ignition switch to ON.

(h) Check for DTCs (See page ).

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.

USE SIMULATION METHOD TO CHECK

7.	REPLACE OCCUPANT CLASSIFICATION ECU

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

HINT:

Perform the inspection using parts from a normal vehicle if possible.

8.	PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(d) Using the Techstream, perform Zero Point Calibration (See page ).

OK:

"Zero Point Calibration is complete." is displayed.

GO TO STEP 11

9.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform Sensitivity Check (See page ).

Standard:

27 to 33 kg (59.5 to 72.8 lb)

GO TO STEP 11

10.

CHECK DTC

(a) Turn the ignition switch to ON.

(b) Clear the DTCs stored in the occupant classification ECU (See page ).

(d) Turn the ignition switch off.

(e) Turn the ignition switch to ON.

(f) Check for DTCs (See page ).

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.

END

11.	REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

12.	PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(d) Using the Techstream, perform Zero Point Calibration (See page ).

OK:

"Zero Point Calibration is complete." is displayed.

13.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform Sensitivity Check (See page ).

Standard:

27 to 33 kg (59.5 to 72.8 lb)

END

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