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Occupant Classification System (Diagnostic Codes & Symptom Tests): Overview Lexus IS III

Airbag 6 illustrations ~576 words

DESCRIPTION

The front occupant classification sensor LH circuit consists of the occupant detection ECU and front occupant classification sensor LH (separate type front seat cushion spring assembly RH).

DTC B1780 is stored when a malfunction is detected in the front occupant classification sensor LH circuit.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1780Front Occupant Classification Sensor LH Circuit MalfunctionThe occupant detection ECU detects a line short, short to ground or B+, or an open in the front occupant classification sensor LH circuit. Front occupant classification sensor LH malfunction Occupant detection ECU malfunctionFront seat wire RH Front occupant classification sensor LH (Separate type front seat cushion spring assembly RH) Occupant detection ECU

Scheme 36

Scheme 36: WIRING DIAGRAM

The rear occupant classification sensor LH circuit consists of the occupant detection ECU and rear occupant classification sensor LH (separate type front seat cushion spring assembly RH).

DTC B1782 is stored when a malfunction is detected in the rear occupant classification sensor LH circuit.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1782Rear Occupant Classification Sensor LH Circuit MalfunctionThe occupant detection ECU detects a line short, short to ground or B+, or an open in the rear occupant classification sensor LH circuit. Rear occupant classification sensor LH malfunction Occupant detection ECU malfunctionFront seat wire RH Rear occupant classification sensor LH (Separate type front seat cushion spring assembly RH) Occupant detection ECU

Scheme 37

Scheme 37: WIRING DIAGRAM

DTC B1785 is stored when the occupant detection ECU receives a collision detection signal sent by the front occupant classification sensor LH if an accident occurs.

DTC B1785 is also stored when the front seat assembly RH is subjected to a strong impact, even if an actual accident did not occur.

If the vehicle was not in a collision, but the occupant detection ECU receives a collision detection signal and stores DTC B1785, the DTC can be cleared by performing Zero Point Calibration and Sensitivity Check.

Therefore, if DTC B1785 is output, first perform Zero Point Calibration and Sensitivity Check.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1785Front Occupant Classification Sensor LH Collision DetectionFront occupant classification sensor LH sensed large load. Separate type front seat cushion spring assembly RH malfunctionFront occupant classification sensor LH (Separate type front seat cushion spring assembly RH)

In sleep mode, the occupant detection ECU reads the condition of each sensor while the engine switch is off.

In this mode, if the occupant detection ECU detects an internal malfunction, DTC B1796 is stored.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1796Sleep Operation Failure of Occupant Classification ECUOccupant detection ECU malfunctionOccupant detection ECU

DTC B1795 is stored when a malfunction is detected in the occupant detection ECU.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1795Occupant Classification ECU MalfunctionOccupant detection ECU malfunctionOccupant detection ECU

DTC B1794 is stored when a malfunction is detected in the occupant detection ECU battery positive line.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1794Open in Occupant Classification ECU Battery Positive LineThe occupant detection ECU receives an open circuit signal in the occupant detection ECU battery positive line. Occupant detection ECU malfunctionBattery Wire harness Occupant detection ECU

Scheme 38

Scheme 38: WIRING DIAGRAM

DTC B1787 is stored when the occupant detection ECU receives a collision detection signal sent by the rear occupant classification sensor LH if an accident occurs.

DTC B1787 is also stored when the front seat assembly RH is subjected to a strong impact, even if an actual accident did not occur.

If the vehicle was not in a collision, but the occupant detection ECU receives a collision detection signal and stores DTC B1787, the DTC can be cleared by performing Zero Point Calibration and Sensitivity Check.

Therefore, if DTC B1787 is output, first perform Zero Point Calibration and Sensitivity Check.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1787Rear Occupant Classification Sensor LH Collision DetectionRear occupant classification sensor LH sensed large load. Separate type front seat cushion spring assembly RH malfunctionRear occupant classification sensor LH (Separate type front seat cushion spring assembly RH)

The airbag sensor assembly communication circuit consists of the occupant detection ECU and airbag sensor assembly.

DTC B1790 is stored when a malfunction is detected in the airbag sensor assembly communication circuit.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1790Center Airbag Sensor Assembly Communication Circuit MalfunctionThe occupant detection ECU detects a line short, short to ground or B+, or an open in the center airbag sensor assembly communication circuit. Occupant detection ECU malfunction Airbag sensor assembly malfunctionFloor wire Front seat wire RH Occupant detection ECU Airbag sensor assembly

Scheme 39

Scheme 39: WIRING DIAGRAM

The occupant classification sensor power supply circuit consists of the occupant detection ECU, front occupant classification sensor LH* and rear occupant classification sensor LH*.

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

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1793Occupant Classification Sensor Power Supply Circuit MalfunctionThe occupant detection ECU detects a line short, short to ground or B+ in the occupant classification sensor power supply circuit. Front occupant classification sensor LH malfunction Rear occupant classification sensor LH malfunction Occupant detection ECU malfunctionFront seat wire RH Front occupant classification sensor LH* Rear occupant classification sensor LH* Occupant detection ECU

HINT

*: The front occupant classification sensor LH and rear occupant classification sensor LH are built into the separate type front seat cushion spring assembly RH.

Scheme 40

Scheme 40: WIRING DIAGRAM

The passenger side buckle switch circuit consists of the occupant detection ECU and passenger side buckle switch (front seat inner belt assembly RH).

DTC B1771 is stored when a malfunction is detected in the passenger side buckle switch circuit.

DTC No.Detection ItemDTC Detection ConditionTrouble Area
B1771Passenger Side Buckle Switch Circuit MalfunctionThe occupant detection ECU detects a line short, short to ground or B+, or an open in the passenger side buckle switch circuit. Passenger side buckle switch malfunction Occupant detection ECU malfunctionFront seat wire RH Passenger side buckle switch (Front seat inner belt assembly RH) Occupant detection ECU

Scheme 41

Scheme 41: WIRING DIAGRAM

The occupant classification system detects the front passenger seat condition. It then displays the instrument panel passenger airbag assembly and lower No. 2 instrument panel airbag assembly condition (activated/not activated) using the passenger airbag ON/OFF indicator.

HINT

Approximately 6 seconds after the engine switch is turned on (IG), the passenger airbag ON/OFF indicator will indicate ON/OFF depending on the conditions listed below.

Front Passenger Seat ConditionPassenger Airbag ON/OFF IndicatorSRS Warning Light
ON IndicatorOFF Indicator
VacantOFFONOFF
Adult is seatedONOFFOFF
Child is seatedOFFONOFF
Child restraint system is installed
Occupant classification system failureOFFONON