Lexus NX manuals

Lexus NX: Short in Side Squib (LH) Circuit (B1825-B1828)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Short in Side Squib (LH) Circuit (B1825-B1828)

DESCRIPTION

The front side squib LH circuit consists of the airbag ECU assembly and front seat airbag assembly LH.

The circuit instructs the SRS to deploy when deployment conditions are met.

These DTCs are stored when a malfunction is detected in the front side squib LH circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1825

Short in Side Squib (LH) Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects a line short circuit signal 5 times in the front side squib LH circuit during the primary check.
  • A front seat airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Front seat airbag assembly LH
  • Airbag ECU assembly

B1826

Open in Side Squib (LH) Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects an open circuit signal in the front side squib LH circuit for 2 seconds.
  • A front seat airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Front seat airbag assembly LH
  • Airbag ECU assembly

B1827

Short in Side Squib (LH) Circuit (to Ground)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to ground signal in the front side squib LH circuit for 0.5 seconds.
  • A front seat airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Front seat airbag assembly LH
  • Airbag ECU assembly

B1828

Short in Side Squib (LH) Circuit (to +B)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to B+ signal in the front side squib LH circuit for 0.5 seconds.
  • A front seat airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Front seat airbag assembly LH
  • 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

HINT:

To perform the simulation method, enter check mode (signal check) with the Techstream (Click here ), and then wiggle each connector of the airbag system or drive the vehicle on various types of road (Click here ).

PROCEDURE

1.

CHECK FRONT SEAT AIRBAG ASSEMBLY LH

(a) Turn the power switch off.

*1

Front Seat Airbag Assembly LH

*2

Airbag ECU Assembly

*3

Connector C

*4

SST

*a

Front view of wire harness connector

(to Front Seat Airbag Assembly LH)

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

(c) Disconnect the connector from the front seat airbag assembly LH.

(d) Connect the red wire side of SST (resistance: 2.1 Ω) to connector C.

CAUTION:

Never connect the tester to the front seat airbag assembly LH for measurement, as this may lead to a serious injury due to airbag deployment.

NOTICE:

  • Do not forcibly insert SST into the terminals of the connector when connecting SST.
  • Insert SST straight into the terminals of the connector.

SST: 09843-18061

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

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

(g) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(h) Turn the power switch off.

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

(j) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTC B1825, B1826, B1827 and B1828 may be output at this time, but they are not related to this check.

(k) Turn the power switch off.

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

(m) Disconnect SST from connector C.

DTC B1825, B1826, B1827 or B1828 is not output.

REPLACE FRONT SEAT AIRBAG ASSEMBLY LH

DTC B1825, B1826, B1827 or B1828 is output.

2.

CHECK CONNECTORS

(a) Disconnect the connectors from the airbag ECU assembly.

(b) Check that the connectors (on the airbag ECU assembly side and front seat airbag assembly LH side) are not damaged.

OK:

The lock button is not disengaged, and the claw of the lock is not deformed or damaged.

*1

Front Seat Airbag Assembly LH

*2

No. 2 Floor Wire

*3

Airbag ECU Assembly
NG

REPLACE NO. 2 FLOOR WIRE
OK

3.

CHECK NO. 2 FLOOR WIRE

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

*1

Front Seat Airbag Assembly LH

*2

No. 2 Floor Wire

*3

Airbag ECU Assembly

*4

Connector C

*a

Front view of wire harness connector

(to Front Seat Airbag Assembly LH)

(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

Qd1-1 (SFL+) - Body ground

Power switch on (IG)

Below 1 V

Qd1-2 (SFL-) - 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) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

Qd1-1 (SFL+) - Qd1-2 (SFL-)

Always

Below 1 Ω

(g) Release the activation prevention mechanism built into connector B.

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Qd1-1 (SFL+) - Qd1-2 (SFL-)

Always

1 MΩ or higher

(i) Restore the released activation prevention mechanism of connector B to its original condition.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Qd1-1 (SFL+) - Body ground

Always

1 MΩ or higher

Qd1-2 (SFL-) - Body ground

Always

1 MΩ or higher
NG

REPLACE NO. 2 FLOOR WIRE
OK

4.

CHECK DTC

(a) Connect the connectors to the front seat airbag assembly LH and airbag ECU assembly.

*1

Front Seat Airbag Assembly LH

*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 B1825, B1826, B1827 and B1828 may be output at this time, but they are not related to this check.

DTC B1825, B1826, B1827 or B1828 is not output

USE SIMULATION METHOD TO CHECK

DTC B1825, B1826, B1827 or B1828 is output

REPLACE AIRBAG ECU ASSEMBLY

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