Lexus NX manuals

Lexus NX: Front Occupant Classification Sensor LH Circuit Malfunction (B1780)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Occupant Classification System / Front Occupant Classification Sensor LH Circuit Malfunction (B1780)

DESCRIPTION

The front occupant classification sensor LH circuit consists of the occupant detection ECU and front occupant classification sensor LH.

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

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1780

Front Occupant Classification Sensor LH Circuit Malfunction
One of the following conditions is met:
  • Occupant detection ECU detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in the front occupant classification sensor LH circuit for 2 seconds.
  • Front occupant classification sensor LH malfunction.
  • Occupant detection ECU malfunction.
  • Front seat adjuster assembly RH (front occupant classification sensor LH)
  • Front seat wire RH
  • Occupant detection ECU

HINT:

  • When DTC B1650/32 is stored as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1780 of the occupant classification system.
  • Use the Techstream to check for DTCs of the occupant detection ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When disconnecting the cable, some systems need to be initialized after the cable is reconnected

Click here

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 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.

Click here

Body Electrical > Occupant Detection > Trouble Codes

HINT:

DTCs other than DTC B1780 may be output at this time, but they are not related to this check.

DTC B1780 is not output

USE SIMULATION METHOD TO CHECK

DTC B1780 is output

2.

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 occupant detection ECU and front occupant classification sensor LH.

Connectors are not properly connected

CONNECT CONNECTORS
Connectors are properly connected

3.

CHECK CONNECTORS

(a) Disconnect the connectors from the occupant detection ECU and front occupant classification sensor LH.

*1

Front Occupant Classification Sensor LH

*2

Occupant Detection ECU

*3

Front Seat Wire RH

(b) Check that the connectors (on the occupant detection ECU side and front occupant classification sensor LH side) are not damaged.

Click here

Connectors are deformed or damaged

REPLACE FRONT SEAT WIRE RH
Connectors are not deformed or damaged

4.

CHECK FRONT SEAT WIRE RH

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

*1

Front Seat Wire RH

*2

Front Occupant Classification Sensor LH

*3

Occupant Detection ECU

*4

Service Wire

*5

Connector C

*6

Connector B

*a

Front view of wire harness connector

(to Front Occupant Classification Sensor LH)

*b

Front view of wire harness connector

(to Occupant Detection ECU)

(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

f14-1 (SVC1) - Body ground

Power switch on (IG)

Below 1 V

f14-3 (SIG1) - Body ground

f14-5 (SGD1) - Body ground

(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 service wires, connect terminals 1 (SVC) and 3 (SGD), and terminals 2 (SIG) and 3 (SGD) of connector C.

NOTICE:

Do not forcibly insert the service wires 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

f14-1 (SVC1) - f14-5 (SGD1)

Always

Below 1 Ω

f14-3 (SIG1) - f14-5 (SGD1)

(h) Disconnect the service wires from connector C.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

f14-1 (SVC1) - f14-5 (SGD1)

Always

1 MΩ or higher

f14-3 (SIG1) - f14-5 (SGD1)

f14-1 (SVC1) - f14-3 (SIG1)

f14-1 (SVC1) - Body ground

f14-3 (SIG1) - Body ground

f14-5 (SGD1) - Body ground
NG

REPLACE FRONT SEAT WIRE RH
OK

5.

CHECK DTC

(a) Connect the connectors to the occupant detection ECU and front occupant classification sensor LH.

(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 > 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.

(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 > Occupant Detection > Trouble Codes

HINT:

DTCs other than DTC B1780 may be output at this time, but they are not related to this check.

DTC B1780 is not output

USE SIMULATION METHOD TO CHECK

DTC B1780 is output

6.

REPLACE OCCUPANT DETECTION ECU

(a) Turn the power switch off.

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

(c) Replace the occupant detection ECU.

Click here

HINT:

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

"Zero Point Calibration is complete." is displayed

7.

PERFORM ZERO POINT CALIBRATION

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

(b) Turn the power switch on (IG)

(c) Perform the zero point calibration.

Click here

"Zero Point Calibration is complete." is not displayed

GO TO STEP 10

"Zero Point Calibration is complete." is displayed

8.

PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check.

Click here

Standard:

27 to 33 kg (59.5 to 72.8 lb)

NG

GO TO STEP 10

OK

9.

CHECK DTC

(a) 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.

(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 > Occupant Detection > Trouble Codes

HINT:

DTCs other than DTC B1780 may be output at this time, but they are not related to this check.

DTC B1780 is not output

END (OCCUPANT DETECTION ECU WAS DEFECTIVE)
DTC B1780 is output

GO TO STEP 10

10.

REPLACE FRONT SEAT ADJUSTER ASSEMBLY RH (FRONT OCCUPANT CLASSIFICATION SENSOR LH)

(a) Turn the power switch off.

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

(c) Replace the front seat adjuster assembly RH.

Click here

HINT:

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

NEXT

11.

PERFORM ZERO POINT CALIBRATION

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

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

(c) Perform the zero point calibration.

Click here

"Zero Point Calibration is complete." is displayed

12.

PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check.

Click here

Standard:

27 to 33 kg (59.5 to 72.8 lb)

NEXT

END (FRONT SEAT ADJUSTER ASSEMBLY RH [FRONT OCCUPANT CLASSIFICATION SENSOR LH] WAS DEFECTIVE)

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