Lexus NX: Short in Curtain Shield Airbag (LH) Squib Circuit (B1835-B1838)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Short in Curtain Shield Airbag (LH) Squib Circuit (B1835-B1838)

DESCRIPTION

The curtain shield squib LH circuit consists of the airbag ECU assembly and curtain shield 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 curtain shield squib LH circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1835

Short in Curtain Shield Airbag (LH) Squib Circuit

One of the following conditions is met:

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

B1836

Open in Curtain Shield Airbag (LH) Squib Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects an open circuit signal in the curtain shield squib LH circuit for 2 seconds.
  • A curtain shield airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Curtain shield airbag assembly LH
  • Airbag ECU assembly

B1837

Short in Curtain Shield Airbag (LH) Squib Circuit (to Ground)

One of the following conditions is met:

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

B1838

Short in Curtain Shield Airbag (LH) Squib Circuit (to +B)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to B+ signal in the curtain shield squib LH circuit for 0.5 seconds.
  • A curtain shield airbag assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Curtain shield 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 CURTAIN SHIELD AIRBAG ASSEMBLY LH

(a) Turn the power switch off.

*1

Curtain Shield Airbag Assembly LH

*2

Airbag ECU Assembly

*3

Connector C

*4

SST

*a

Front view of wire harness connector

(to Curtain Shield Airbag Assembly LH)

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

(c) Disconnect the connectors from the curtain shield airbag assembly LH.

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

CAUTION:

Never connect the tester to the curtain shield 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 B1835, B1836, B1837 and B1838 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 B1835, B1836, B1837 or B1838 is not output

REPLACE CURTAIN SHIELD AIRBAG ASSEMBLY LH

DTC B1835, B1836, B1837 or B1838 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 curtain shield 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

Curtain Shield 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

Curtain Shield Airbag Assembly LH

*2

No. 2 Floor Wire

*3

Airbag ECU Assembly

*4

Connector C

*a

Front view of wire harness connector

(to Curtain Shield 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

Q10-1 (ICL+) - Body ground

Power switch on (IG)

Below 1 V

Q10-2 (ICL-) - 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

Q10-1 (ICL+) - Q10-2 (ICL-)

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

Q10-1 (ICL+) - Q10-2 (ICL-)

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

Q10-1 (ICL+) - Body ground

Always

1 MΩ or higher

Q10-2 (ICL-) - Body ground

Always

1 MΩ or higher

NG

REPLACE NO. 2 FLOOR WIRE

OK

4.

CHECK DTC

(a) Connect the connectors to the curtain shield airbag assembly LH and airbag ECU assembly.

*1

Curtain Shield 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 B1835, B1836, B1837 and B1838 may be output at this time, but they are not related to this check.

DTC B1835, B1836, B1837 or B1838 is not output

USE SIMULATION METHOD TO CHECK

DTC B1835, B1836, B1837 or B1838 is output

REPLACE AIRBAG ECU ASSEMBLY

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DIAGNOSIS SYSTEM CHECK DLC3 (a) Check the DLC3. Click here INSPECT AUXILIARY BATTERY VOLTAGE (a) Measure the auxiliary battery voltage. Standard voltage: 11 to 14 V (power switch off) If the voltage is below 11 V, recharge or replace the auxiliary battery.

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