Toyota 4Runner: Occupant Classification Sensor Power Supply Circuit Malfunction (B1793)

Toyota 4Runner Service Manual / Vehicle Interior / 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 stored when a malfunction is detected in the occupant classification sensor power supply circuit.

DTC Code	DTC Detection Condition	Trouble Area
B1793	One of the following conditions is met: Occupant classification ECU detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in the occupant classification sensor power supply circuit for 2 seconds. Open circuit in the occupant classification sensor wire harness. Occupant classification ECU malfunction.	Separate type front seat cushion spring RH (Occupant classification sensors) Front seat wire RH Occupant classification ECU

HINT:

When DTC B1650/32 is stored as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1793 of the occupant classification system.
Use the Techstream to check for DTCs of the occupant classification ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the front seat RH installation bolts to see the undersurface of the seat cushion.
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 problems, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

1.	CHECK FOR DTC

(a) Turn the ignition switch to ON, and wait for at least 60 seconds.

(b) Clear the DTCs stored in memory (See page
).

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.

(d) Turn the ignition switch to ON, and wait for at least 60 seconds.

(e) Using the Techstream, check for DTCs of the occupant classification ECU (See page ).

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.

USE SIMULATION METHOD TO CHECK

2.	CHECK CONNECTION OF CONNECTOR

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

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

OK:

Connectors are properly connected.

CONNECT CONNECTOR

3.	CHECK CONNECTOR

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

(b) Check that the connectors (on the occupant classification ECU side and occupant classification sensor side) are not damaged (See page ).

OK:

Connectors are not deformed or damaged.

REPLACE FRONT SEAT WIRE RH

4.	CHECK FRONT SEAT WIRE RH

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

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)	-	-

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
a10-11 (SVC1) - Body ground	Ignition switch ON	Below 1 V
a10-12 (SVC2) - Body ground
a10-5 (SVC3) - Body ground
a10-6 (SVC4) - Body ground

(d) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
a10-11 (SVC1) - a8-1 (SVC1)	Always	Below 1 Ω
a10-12 (SVC2) - a6-1 (SVC2)
a10-5 (SVC3) - a11-1 (SVC3)
a10-6 (SVC4) - a5-1 (SVC4)
a10-11 (SVC1) - a10-12 (SVC2)	Always	1 MΩ or higher
a10-11 (SVC1) - a10-5 (SVC3)
a10-11 (SVC1) - a10-6 (SVC4)
a10-12 (SVC2) - a10-5 (SVC3)
a10-12 (SVC2) - a10-6 (SVC4)
a10-5 (SVC3) - a10-6 (SVC4)
a10-11 (SVC1) - Body ground
a10-12 (SVC2) - Body ground
a10-5 (SVC3) - Body ground
a10-6 (SVC4) - Body ground

REPLACE FRONT SEAT WIRE RH

5.	CHECK FOR DTC

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

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

(d) Clear the DTCs stored in memory (See page
).

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.

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 60 seconds.

(g) Using the Techstream, check for DTCs of the occupant classification ECU (See page ).

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.

USE SIMULATION METHOD TO CHECK

6.	REPLACE OCCUPANT CLASSIFICATION ECU

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

HINT:

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

7.	PERFORM ZERO POINT CALIBRATION

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

(b) Turn the ignition switch to ON, and wait for at least 60 seconds.

OK:

"Zero Point Calibration is complete." is displayed.

GO TO STEP 10

8.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page ).

Standard range:

27 to 33 kg (59.5 to 72.8 lb)

GO TO STEP 10

9.	CHECK FOR DTC

(a) Clear the DTCs stored in memory (See page
).

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.

(b) Turn the ignition switch off.

(d) Using the Techstream, check for DTCs of the occupant classification ECU (See page ).

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.

END

10.	REPLACE SEPARATE TYPE FRONT SEAT CUSHION SPRING ASSEMBLY

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

(1) Replace the separate type front seat cushion spring RH (See page ).

(d) for Power Seat:

(1) Replace the separate type front seat cushion spring RH (See page ).

HINT:

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

11.	PERFORM ZERO POINT CALIBRATION

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

(b) Turn the ignition switch to ON, and wait for at least 60 seconds.

OK:

"Zero Point Calibration is complete." is displayed.

12.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page ).

Standard range:

27 to 33 kg (59.5 to 72.8 lb)

END

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