Lexus NX: Occupant Classification System Malfunction (B1650)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Occupant Classification System Malfunction (B1650)

DESCRIPTION

The occupant classification system circuit consists of the airbag ECU assembly and occupant detection ECU.

If the airbag ECU assembly receives signals from the occupant detection ECU, it determines whether the instrument panel passenger airbag, front seat airbag RH and front seat outer belt assembly should be operated.

DTC B1650 is stored when a malfunction is detected in the occupant classification system circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1650

Occupant Classification System Malfunction

One of the following conditions is met:
  • An occupant classification system malfunction.
  • The airbag ECU assembly detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the occupant classification system circuit for 2 seconds.
  • An airbag ECU assembly malfunction.
  • Floor wire
  • Front seat wire RH
  • Occupant classification system
  • Airbag ECU assembly

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • After the power switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.

    Click here

  • When disconnecting and reconnecting the auxiliary battery

    Click here

    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

    Click here

  • After replacing the airbag ECU assembly, refer to initialization.

    Click here

PROCEDURE

1.

CHECK DTC

(a) Turn the power switch on (IG), and wait for at least 60 seconds.

(b) Clear the DTCs.

Click here

Body Electrical > Occupant Detection > Clear DTCs

HINT:

  • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.
  • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.

(c) Turn the power switch off.

(d) Turn the power switch on (IG), and wait for at least 60 seconds.

(e) Check for DTCs of the occupant detection ECU.

Click here

Body Electrical > Occupant Detection > Trouble Codes
DTC is output

GO TO OCCUPANT CLASSIFICATION SYSTEM

DTC is not output

2.

CHECK DTC

(a) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(b) Turn the power switch off.

(c) Turn the power switch on (IG), and wait for at least 60 seconds.

(d) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTC B1650 may be output at this time, but they are not related to this check.

DTC B1650 is not output

USE SIMULATION METHOD TO CHECK

DTC B1650 is output

3.

CHECK CONNECTION OF CONNECTORS

(a) Turn the power switch off.

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

(c) Check that the connectors are properly connected to the airbag ECU assembly and occupant detection ECU.

Connectors are not properly connected

CONNECT CONNECTORS PROPERLY

Connectors are properly connected

4.

CHECK CONNECTORS

(a) Disconnect the connectors from the airbag ECU assembly and occupant detection ECU.

*1

Occupant Detection ECU

*2

Airbag ECU Assembly

*3

Front Seat Wire RH

*4

Floor Wire

(b) Check that the connectors (on the airbag ECU assembly side and occupant detection ECU side) are not damaged.

Connectors are deformed or damaged

REPLACE FRONT SEAT WIRE RH OR FLOOR WIRE

Connectors are not deformed or damaged

5.

CHECK OCCUPANT DETECTION ECU CIRCUIT

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

*1

Occupant Detection ECU

*2

Airbag ECU Assembly

*3

Connector E

*4

Connector B

*5

Service Wire

*a

Front view of wire harness connector

(to Occupant Detection ECU)

*b

Rear view of wire harness connector

(to Airbag ECU Assembly)

(b) Turn the power switch on (IG).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

f15-7 (FSR+) - Body ground

Power switch on (IG)

Below 1 V

f15-4 (FSR-) - Body ground

Power switch on (IG)

Below 1 V

(d) Turn the power switch off.

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

(f) Using a service wire, connect terminals 9 (FSR+) and 17 (FSR-) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

f15-7 (FSR+) - f15-4 (FSR-)

Always

Below 1 Ω

(h) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

f15-7 (FSR+) - f15-4 (FSR-)

Always

1 MΩ or higher

f15-7 (FSR+) - Body ground

Always

1 MΩ or higher

f15-4 (FSR-) - Body ground

Always

1 MΩ or higher

NG

GO TO STEP 7

OK

6.

CHECK DTC

(a) Connect the connectors to the airbag ECU assembly and occupant detection ECU.

*1

Occupant Detection ECU

*2

Airbag ECU Assembly

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

(c) Turn the power switch on (IG), and wait for at least 60 seconds.

(d) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the power switch off.

(f) Turn the power switch on (IG), and wait for at least 60 seconds.

(g) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTC B1650 may be output at this time, but they are not related to this check.

DTC B1650 is output

REPLACE AIRBAG ECU ASSEMBLY

DTC B1650 is not output

USE SIMULATION METHOD TO CHECK

7.

CHECK FRONT SEAT WIRE RH

(a) Disconnect the front seat wire RH connector from the floor wire.

*1

Front Seat Wire RH

*2

Floor Wire

*3

Occupant Detection ECU

*4

Airbag ECU Assembly

*5

Service Wire

*6

Connector E

*7

Connector D

*a

Front view of wire harness connector

(to Occupant Detection ECU)

*b

Front view of wire harness connector

(to Floor Wire)

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

(c) Turn the power switch on (IG).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

Pf2-7 (FSR+) - Body ground

Power switch on (IG)

Below 1 V

Pf2-3 (FSR-) - Body ground

Power switch on (IG)

Below 1 V

(e) Turn the power switch off.

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

(g) Using a service wire, connect terminals 7 (FSR+) and 4 (FSR-) of connector E.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Pf2-7 (FSR+) - Pf2-3 (FSR-)

Always

Below 1 Ω

(i) Disconnect the service wire from connector E.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Pf2-7 (FSR+) - Pf2-3 (FSR-)

Always

1 MΩ or higher

Pf2-7 (FSR+) - Body ground

Always

1 MΩ or higher

Pf2-3 (FSR-) - Body ground

Always

1 MΩ or higher

OK

REPLACE FLOOR WIRE

NG

REPLACE FRONT SEAT WIRE RH

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