SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM: DESCRIPTION (2008 Sequoia)

Last Modified: 11-29-2007		1.6 C
Service Category: Vehicle Interior	Section: Supplemental Restraint Systems
Model Year: 2008	Model: Sequoia	Doc ID: RM00000158100AX
Title: SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM: DESCRIPTION (2008 Sequoia)

DTC

B1793

Occupant Classification Sensor Power Supply Circuit Malfunction

DESCRIPTION

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

DTC B1793 is stored when a malfunction is detected in the occupant detection sensor power supply circuit.

DTC Code	DTC Detection Condition	Trouble Area
B1793	One of following conditions is met: Occupant classification ECU receives line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in occupant detection sensor power supply circuit for 2 seconds Open circuit in occupant detection sensor wire harness Occupant classification ECU malfunction	Front seat assembly RH (Occupant detection sensors) Front seat wire RH Occupant classification ECU

HINT:

When DTC B1650/32 is detected 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

INSPECTION PROCEDURE

NOTICE:

After the ignition switch is turned off, the navigation system requires approximately 90 seconds to record various types of memory and settings. As a result, after turning the ignition switch off, wait 90 seconds or more before disconnecting the cable from the negative (-) battery terminal.

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 any DTCs stored in the memory .

HINT:

First clear DTCs stored in the occupant classification ECU and then 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 .

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.

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 the occupant detection sensors.

OK:

Connectors are properly connected.

3.	CHECK CONNECTOR

(a) Check that the connectors (on the occupant classification ECU side and the occupant detection sensors side) are not damaged .

OK:

Connectors are not deformed or damaged.

4.	CHECK FRONT SEAT WIRE RH

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

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

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
W1-11 (SVC1) - Body ground	Ignition switch ON	Below 1 V
W1-12 (SVC2) - Body ground
W1-5 (SVC3) - Body ground
W1-6 (SVC4) - Body ground

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

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
W1-11 (SVC1) - W2-1 (SVC1)	Ignition switch ON	Below 1 Ω
W1-12 (SVC2) - W3-1 (SVC2)
W1-5 (SVC3) - W4-1 (SVC3)
W1-6 (SVC4) - W5-1 (SVC4)

(f) Turn the ignition switch off.

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
W1-11 (SVC1) - Body ground	Always	1 MΩ or higher
W1-12 (SVC2) - Body ground
W1-5 (SVC3) - Body ground
W1-6 (SVC4) - Body ground
W1-11 (SVC1) - W1-12 (SVC2)
W1-12 (SVC2) - W1-5 (SVC3)
W1-12 (SVC2) - W1-6 (SVC4)
W1-11 (SVC1) - W1-5 (SVC3)

5.	CHECK FOR DTC

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

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

(d) Clear any DTCs stored in the memory .

HINT:

First clear DTCs stored in the occupant classification ECU and then 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 .

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.

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) Connect the Techstream to the DLC3.

(d) Using the Techstream, perform the zero point calibration .

8.	PERFORM SENSITIVITY CHECK

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

Standard range:

27 to 33 kg (59.5 to 72.8 lb)