Lexus NX: Short in Knee Airbag (D Side) Squib Circuit (B1860-B1863)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Short in Knee Airbag (D Side) Squib Circuit (B1860-B1863)

DESCRIPTION

The driver side knee squib circuit consists of the airbag ECU assembly and lower No. 1 instrument panel airbag assembly.

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

These DTCs are stored when a malfunction is detected in the driver side knee squib circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1860

Short in Knee Airbag (D Side) Squib Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects a line short circuit signal 5 times in the driver side knee squib circuit during the primary check.
  • A lower No. 1 instrument panel airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Lower No. 1 instrument panel airbag assembly
  • Airbag ECU assembly

B1861

Open in Knee Airbag (D Side) Squib Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects an open circuit signal in the driver side knee squib circuit for 2 seconds.
  • A lower No. 1 instrument panel airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Lower No. 1 instrument panel airbag assembly
  • Airbag ECU assembly

B1862

Short in Knee Airbag (D Side) Squib Circuit (to Ground)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to ground signal in the driver side knee squib circuit for 0.5 seconds.
  • A lower No. 1 instrument panel airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Lower No. 1 instrument panel airbag assembly
  • Airbag ECU assembly

B1863

Short in Knee Airbag (D Side) Squib Circuit (to +B)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to B+ signal in the driver side knee squib circuit for 0.5 seconds.
  • A lower No. 1 instrument panel airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Lower No. 1 instrument panel airbag assembly
  • 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 LOWER NO. 1 INSTRUMENT PANEL AIRBAG ASSEMBLY

(a) Turn the power switch off.

*1

Lower No. 1 Instrument Panel Airbag Assembly

*2

Airbag ECU Assembly

*3

Connector C

*4

SST

*a

Front view of wire harness connector

(to Lower No. 1 Instrument Panel Airbag Assembly)

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

(c) Disconnect the connector from the lower No. 1 instrument panel airbag assembly.

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

CAUTION:

Never connect the tester to the lower No. 1 instrument panel airbag assembly 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 B1860, B1861, B1862 and B1863 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 B1860, B1861, B1862 or B1863 is not output

REPLACE LOWER NO. 1 INSTRUMENT PANEL AIRBAG ASSEMBLY

DTC B1860, B1861, B1862 or B1863 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 lower No. 1 instrument panel airbag assembly side) are not damaged.

OK:

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

*1

Lower No. 1 Instrument Panel Airbag Assembly

*2

Instrument Panel Wire

*3

Airbag ECU Assembly

NG

REPLACE INSTRUMENT PANEL WIRE

OK

3.

CHECK INSTRUMENT PANEL WIRE

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

*1

Lower No. 1 Instrument Panel Airbag Assembly

*2

Instrument Panel Wire

*3

Airbag ECU Assembly

*4

Connector C

*a

Front view of wire harness connector

(to Lower No. 1 Instrument Panel Airbag 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

I18-1 (DK+) - Body ground

Power switch on (IG)

Below 1 V

I18-2 (DK-) - 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

I18-1 (DK+) - I18-2 (DK-)

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

I18-1 (DK+) - I18-2 (DK-)

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

I18-1 (DK+) - Body ground

Always

1 MΩ or higher

I18-2 (DK-) - Body ground

Always

1 MΩ or higher

NG

REPLACE INSTRUMENT PANEL WIRE

OK

4.

CHECK DTC

(a) Connect the connectors to the lower No. 1 instrument panel airbag assembly and airbag ECU assembly.

*1

Lower No. 1 Instrument Panel Airbag Assembly

*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 B1860, B1861, B1862 and B1863 may be output at this time, but they are not related to this check.

DTC B1860, B1861, B1862 or B1863 is not output

USE SIMULATION METHOD TO CHECK

DTC B1860, B1861, B1862 or B1863 is output

REPLACE AIRBAG ECU ASSEMBLY

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