Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Short in Knee Airbag (D Side) Squib Circuit (B1860-B1863)

DESCRIPTION

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

The airbag sensor assembly uses this circuit to deploy the airbag when deployment conditions are met.

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

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Test Mode / Check Mode
B1860	Short in Knee Airbag (D Side) Squib Circuit	The airbag sensor assembly detects a line short in the driver side knee airbag squib during the primary check. Driver side knee airbag squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Driver side knee airbag squib (Lower No. 1 instrument panel airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1861	Open in Knee Airbag (D Side) Squib Circuit	The airbag sensor assembly detects an open in the driver side knee airbag squib. Driver side knee airbag squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Driver side knee airbag squib (Lower No. 1 instrument panel airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1862	Short in Knee Airbag (D Side) Squib Circuit (to Ground)	The airbag sensor assembly detects a short to ground in the driver side knee airbag squib. Driver side knee airbag squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Driver side knee airbag squib (Lower No. 1 instrument panel airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1863	Short in Knee Airbag (D Side) Squib Circuit (to +B)	The airbag sensor assembly detects a short to B+ in the driver side knee airbag squib. Driver side knee airbag squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Driver side knee airbag squib (Lower No. 1 instrument panel airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

Click here

PROCEDURE

1.	CHECK CONNECTORS

(a) Turn the engine switch off.

*1 Lower No. 1 Instrument Panel Airbag Assembly *2 Airbag Sensor Assembly *3 Instrument Panel Wire

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connectors are properly connected to the lower No. 1 instrument panel airbag assembly and airbag sensor assembly.

OK:

The connectors are properly connected.

HINT:

If the connectors are not properly connected, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the lower No. 1 instrument panel airbag assembly and airbag sensor assembly.

(e) Check that the terminals of the connectors are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

(f) Check that the instrument panel wire connector (on the lower No. 1 instrument panel airbag assembly side) is not loose, deformed or damaged.

OK:

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

(g) Check that the short springs of the activation prevention mechanism of the instrument panel wire connector are not deformed or damaged.

OK:

The short springs are not deformed or damaged.

NG

REPLACE INSTRUMENT PANEL WIRE

OK

2.	CHECK LOWER NO. 1 INSTRUMENT PANEL AIRBAG ASSEMBLY

(a) Connect the connector to the airbag sensor assembly.

*1 Lower No. 1 Instrument Panel Airbag Assembly *2 Airbag Sensor Assembly *a Front view of wire harness connector (to Lower No. 1 Instrument Panel Airbag Assembly)

(b) Connect SST (resistance 2.1 Ω) to connector C.

CAUTION:

Never connect a tester to the lower No. 1 instrument panel airbag assembly for measurement, as this may lead to a serious injury due to airbag deployment.

SST: 09843-18061

(c) Connect the cable to the negative (-) battery terminal.

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

(e) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the engine switch off.

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

(h) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1860, B1861, B1862 or B1863 is not output.

HINT:

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

(i) Turn the engine switch off.

(j) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(k) Disconnect SST from connector C.

OK

REPLACE LOWER NO. 1 INSTRUMENT PANEL AIRBAG ASSEMBLY

NG

3.	CHECK INSTRUMENT PANEL WIRE

(a) Disconnect the instrument panel wire from the airbag sensor assembly.

*1 Lower No. 1 Instrument Panel Airbag Assembly *2 Airbag Sensor Assembly *3 Instrument Panel Wire *a Front view of wire harness connector (to Lower No. 1 Instrument Panel Airbag Assembly)

(b) Check for a short to B+ in the circuit.

(1) Connect the cable to the negative (-) battery terminal.

(2) Turn the engine switch on (IG).

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
J6-1 (DK+) - Body ground	Engine switch on (IG)	Below 1 V
J6-2 (DK-) - Body ground	Engine switch on (IG)	Below 1 V

(4) Turn the engine switch off.

(5) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check for an open in the circuit.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J6-1 (DK+) - J6-2 (DK-)	Always	Below 1 Ω

(d) Check for a short to ground in the circuit.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J6-1 (DK+) - Body ground	Always	1 MΩ or higher
J6-2 (DK-) - Body ground	Always	1 MΩ or higher

(e) Check for a short in the circuit.

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J6-1 (DK+) - J6-2 (DK-)	Always	1 MΩ or higher

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

NG

REPLACE INSTRUMENT PANEL WIRE

OK

4.

CHECK DTC

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

*1 Lower No. 1 Instrument Panel Airbag Assembly *2 Airbag Sensor Assembly

(b) Connect the cable to the negative (-) battery terminal.

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

(d) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the engine switch off.

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

(g) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1860, B1861, B1862 or B1863 is not output.

HINT:

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

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE AIRBAG SENSOR ASSEMBLY