Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Short in P Squib Circuit (B1805-B1808)

DESCRIPTION

The front passenger squib circuit consists of the airbag sensor assembly and instrument panel passenger 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 front passenger squib circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Test Mode / Check Mode
B1805	Short in P Squib Circuit	The airbag sensor assembly detects a line short in the front passenger squib circuit during the primary check. Front passenger squib malfunction Airbag sensor assembly malfunction	Instrument panel wire No. 2 instrument panel wire Front passenger squib (Instrument panel passenger airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1806	Open in P Squib Circuit	The airbag sensor assembly detects an open in the front passenger squib circuit. Front passenger squib malfunction Airbag sensor assembly malfunction	Instrument panel wire No. 2 instrument panel wire Front passenger squib (Instrument panel passenger airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1807	Short in P Squib Circuit (to Ground)	The airbag sensor assembly detects a short to ground in the front passenger squib circuit. Front passenger squib malfunction Airbag sensor assembly malfunction	Instrument panel wire No. 2 instrument panel wire Front passenger squib (Instrument panel passenger airbag assembly) Airbag sensor assembly	Comes on	Applies to check mode
B1808	Short in P Squib Circuit (to +B)	The airbag sensor assembly detects a short to B+ in the front passenger squib circuit. Front passenger squib malfunction Airbag sensor assembly malfunction	Instrument panel wire No. 2 instrument panel wire Front passenger squib (Instrument panel passenger 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 Instrument Panel Passenger Airbag Assembly *2 Airbag Sensor Assembly *3 No. 2 Instrument Panel Wire *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 instrument panel passenger airbag assembly and airbag sensor assembly. Also check that the connectors that link the instrument panel wire and No. 2 instrument panel wire are properly connected.

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 instrument panel passenger airbag assembly and airbag sensor assembly. Also disconnect the instrument panel wire from the No. 2 instrument panel wire.

(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 No. 2 instrument panel wire connector (on the instrument panel passenger 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 mechanisms of the instrument panel wire connector and No. 2 instrument panel wire connector are not deformed or damaged.

OK:

The short springs are not deformed or damaged.

NG

REPLACE WIRE HARNESS

OK

2.	CHECK INSTRUMENT PANEL PASSENGER AIRBAG ASSEMBLY

(a) Connect the instrument panel wire to the No. 2 instrument panel wire and airbag sensor assembly.

*1 Instrument Panel Passenger Airbag Assembly *2 Airbag Sensor Assembly *a Front view of wire harness connector (to Instrument Panel Passenger Airbag Assembly) *b Color: Orange

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

CAUTION:

Never connect a tester to the instrument panel passenger 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 B1805, B1806, B1807 or B1808 is not output.

HINT:

Codes other than DTCs B1805, B1806, B1807 and B1808 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 INSTRUMENT PANEL PASSENGER AIRBAG ASSEMBLY

NG

3.	CHECK FRONT PASSENGER SQUIB CIRCUIT

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

*1 Instrument Panel Passenger Airbag Assembly *2 Airbag Sensor Assembly *a Front view of wire harness connector (to Instrument Panel Passenger Airbag Assembly) *b Color: Orange

(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
I2-2 (P+) - Body ground	Engine switch on (IG)	Below 1 V
I2-1 (P-) - 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
I2-2 (P+) - I2-1 (P-)	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
I2-2 (P+) - Body ground	Always	1 MΩ or higher
I2-1 (P-) - 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
I2-2 (P+) - I2-1 (P-)	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 instrument panel passenger airbag assembly and airbag sensor assembly.

*1 Instrument Panel Passenger 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 B1805, B1806, B1807 or B1808 is not output.

HINT:

Codes other than DTCs B1805, B1806, B1807 and B1808 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 No. 2 instrument panel wire from the instrument panel wire.

*1 Instrument Panel Passenger Airbag Assembly *2 Airbag Sensor Assembly *3 No. 2 Instrument Panel Wire *4 Instrument Panel Wire *a Front view of wire harness connector (to No. 2 Instrument Panel Wire)

(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
JI1-1 (P+) - Body ground	Engine switch on (IG)	Below 1 V
JI1-2 (P-) - 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
JI1-1 (P+) - JI1-2 (P-)	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
JI1-1 (P+) - Body ground	Always	1 MΩ or higher
JI1-2 (P-) - 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
JI1-1 (P+) - JI1-2 (P-)	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 NO. 2 INSTRUMENT PANEL WIRE

(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 I2-2 (P+) - Body ground Engine switch on (IG) Below 1 V I2-1 (P-) - 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 Instrument Panel Passenger Airbag Assembly *2 Airbag Sensor Assembly *3 No. 2 Instrument Panel Wire *4 Instrument Panel Wire *a Front view of wire harness connector (to Instrument Panel Passenger Airbag Assembly) *b Color: Orange

(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
I2-2 (P+) - I2-1 (P-)	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
I2-2 (P+) - Body ground	Always	1 MΩ or higher
I2-1 (P-) - 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
I2-2 (P+) - I2-1 (P-)	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 NO. 2 INSTRUMENT PANEL WIRE