Lexus NX manuals

Lexus NX: Short in P Squib Circuit (B1805-B1808)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Short in P Squib Circuit (B1805-B1808)

DESCRIPTION

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

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

These DTCs are stored when a malfunction is detected in the front passenger side squib circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1805

Short in P Squib Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects a line short circuit signal 5 times in the front passenger side squib circuit during the primary check.
  • A instrument panel passenger airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • No. 2 instrument panel wire
  • Instrument panel passenger airbag assembly
  • Airbag ECU assembly

B1806

Open in P Squib Circuit

One of the following conditions is met:

  • The airbag ECU assembly detects an open circuit signal in the front passenger side squib circuit for 2 seconds.
  • A instrument panel passenger airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • No. 2 instrument panel wire
  • Instrument panel passenger airbag assembly
  • Airbag ECU assembly

B1807

Short in P Squib Circuit (to Ground)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to ground signal in the front passenger side squib circuit for 0.5 seconds.
  • A instrument panel passenger airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • No. 2 instrument panel wire
  • Instrument panel passenger airbag assembly
  • Airbag ECU assembly

B1808

Short in P Squib Circuit (to +B)

One of the following conditions is met:

  • The airbag ECU assembly detects a short circuit to B+ signal in the front passenger side squib circuit for 0.5 seconds.
  • A instrument panel passenger airbag assembly malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • No. 2 instrument panel wire
  • Instrument panel passenger 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 INSTRUMENT PANEL PASSENGER AIRBAG ASSEMBLY

(a) Turn the power switch off.

*1

Instrument Panel Passenger Airbag Assembly

*2

Airbag ECU Assembly

*3

Connector E

*4

SST

*a

Front view of wire harness connector

(to Instrument Panel Passenger Airbag Assembly)

*b

Color: Orange

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

(c) Disconnect the connector from the instrument panel passenger airbag assembly.

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

CAUTION:

Never connect the tester to the instrument panel passenger 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 B1805, B1806, B1807 and B1808 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 E.

DTC B1805, B1806, B1807 or B1808 is not output

REPLACE INSTRUMENT PANEL PASSENGER AIRBAG ASSEMBLY

DTC B1805, B1806, B1807 or B1808 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 instrument panel passenger 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

Instrument Panel Passenger Airbag Assembly

*2

Airbag ECU Assembly

*3

No. 2 Instrument Panel Wire

*4

Instrument Panel Wire
NG

REPLACE INSTRUMENT PANEL WIRE OR NO. 2 INSTRUMENT PANEL WIRE
OK

3.

CHECK FRONT PASSENGER SIDE SQUIB CIRCUIT

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

*1

Instrument Panel Passenger Airbag Assembly

*2

Airbag ECU Assembly

*3

Connector E

*a

Front view of wire harness connector

(to Instrument Panel Passenger Airbag Assembly)

*b

Color: Orange

(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

H2-2 (P+) - Body ground

Power switch on (IG)

Below 1 V

H2-1 (P-) - 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

H2-2 (P+) - H2-1 (P-)

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

H2-2 (P+) - H2-1 (P-)

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

H2-2 (P+) - Body ground

Always

1 MΩ or higher

H2-1 (P-) - Body ground

Always

1 MΩ or higher
NG

GO TO STEP 5

OK

4.

CHECK DTC

(a) Connect the connectors to the instrument panel passenger airbag assembly and airbag ECU assembly.

*1

Instrument Panel Passenger 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 B1805, B1806, B1807 and B1808 may be output at this time, but they are not related to this check.

DTC B1805, B1806, B1807 or B1808 is not output

USE SIMULATION METHOD TO CHECK

DTC B1805, B1806, B1807 or B1808 is output

REPLACE AIRBAG ECU ASSEMBLY

5.

CHECK INSTRUMENT PANEL WIRE

(a) Disconnect the instrument panel wire connector from the No. 2 instrument panel wire.

*1

Instrument Panel Passenger Airbag Assembly

*2

No. 2 Instrument Panel Wire

*3

Instrument Panel Wire

*4

Airbag ECU Assembly

*5

Connector C

*a

Front view of wire harness connector

(to No. 2 Instrument Panel Wire)

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

(c) Turn the power switch on (IG).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

IH1-1 (P+) - Body ground

Power switch on (IG)

Below 1 V

IH1-2 (P-) - Body ground

Power switch on (IG)

Below 1 V

(e) Turn the power switch off.

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IH1-1 (P+) - IH1-2 (P-)

Always

Below 1 Ω

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

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IH1-1 (P+) - IH1-2 (P-)

Always

1 MΩ or higher

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IH1-1 (P+) - Body ground

Always

1 MΩ or higher

IH1-2 (P-) - Body ground

Always

1 MΩ or higher
OK

REPLACE NO. 2 INSTRUMENT PANEL WIRE
NG

REPLACE INSTRUMENT PANEL WIRE

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