Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Short in D Squib Circuit (B1800-B1803)

DESCRIPTION

The driver squib circuit consists of the airbag sensor assembly, spiral cable sub-assembly and horn button 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 squib circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Test Mode / Check Mode
B1800	Short in D Squib Circuit	The airbag sensor assembly detects a line short in the driver squib circuit during the primary check. Spiral cable sub-assembly malfunction Driver squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Spiral cable sub-assembly Driver squib (Horn button assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1801	Open in D Squib Circuit	The airbag sensor assembly detects an open in the driver squib circuit. Spiral cable sub-assembly malfunction Driver squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Spiral cable sub-assembly Driver squib (Horn button assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1802	Short in D Squib Circuit (to Ground)	The airbag sensor assembly detects a short to ground in the driver squib circuit. Spiral cable sub-assembly malfunction Driver squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Spiral cable sub-assembly Driver squib (Horn button assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1803	Short in D Squib Circuit (to +B)	The airbag sensor assembly detects a short to B+ in the driver squib circuit. Spiral cable sub-assembly malfunction Driver squib malfunction Airbag sensor assembly malfunction	Instrument panel wire Spiral cable sub-assembly Driver squib (Horn button 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 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag Sensor Assembly *4 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 horn button assembly, spiral cable sub-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 horn button assembly, spiral cable sub-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 spiral cable sub-assembly connector (on the horn button 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 mechanisms of the instrument panel wire connector and spiral cable sub-assembly connector are not deformed or damaged.

OK:

The short springs are not deformed or damaged.

NG

REPLACE WIRE HARNESS

OK

2.	CHECK HORN BUTTON ASSEMBLY

(a) Connect the instrument panel wire to the airbag sensor assembly and spiral cable sub-assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag Sensor Assembly *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(b) Connect SST (resistance 2.1 Ω) to connector E (light green connector).

CAUTION:

Never connect a tester to the horn button 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 B1800, B1801, B1802 or B1803 is not output.

HINT:

Codes other than DTCs B1800, B1801, B1802 and B1803 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 E.

OK

REPLACE HORN BUTTON ASSEMBLY

NG

3.	CHECK DRIVER SQUIB CIRCUIT

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

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag Sensor Assembly *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(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
z16-2 (D+) - Body ground	Engine switch on (IG)	Below 1 V
z16-1 (D-) - 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
z16-2 (D+) - z16-1 (D-)	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
z16-2 (D+) - Body ground	Always	1 MΩ or higher
z16-1 (D-) - 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.

Click here

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
z16-2 (D+) - z16-1 (D-)	Always	1 MΩ or higher

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

NG

GO TO STEP 5

OK

4.

CHECK DTC

(a) Connect the connectors to the horn button assembly and airbag sensor assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 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 B1800, B1801, B1802 or B1803 is not output.

HINT:

Codes other than DTCs B1800, B1801, B1802 and B1803 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

5.	CHECK INSTRUMENT PANEL WIRE

(a) Disconnect the instrument panel wire from the spiral cable sub-assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag Sensor Assembly *4 Instrument Panel Wire *a Front view of wire harness connector (to Spiral Cable Sub-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
J30-1 (D+) - Body ground	Engine switch on (IG)	Below 1 V
J30-2 (D-) - 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
J30-1 (D+) - J30-2 (D-)	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
J30-1 (D+) - Body ground	Always	1 MΩ or higher
J30-2 (D-) - 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.

Click here

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J30-1 (D+) - J30-2 (D-)	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

6.	CHECK SPIRAL CABLE SUB-ASSEMBLY

(a) 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 z16-2 (D+) - Body ground Engine switch on (IG) Below 1 V z16-1 (D-) - 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.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag Sensor Assembly *4 Instrument Panel Wire *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(b) 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
z16-2 (D+) - z16-1 (D-)	Always	Below 1 Ω

(c) 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
z16-2 (D+) - Body ground	Always	1 MΩ or higher
z16-1 (D-) - Body ground	Always	1 MΩ or higher

(d) Check for a short in the circuit.

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

Click here

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
z16-2 (D+) - z16-1 (D-)	Always	1 MΩ or higher

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

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE SPIRAL CABLE SUB-ASSEMBLY