Lexus NX: Front Airbag Sensor Lost Communication (LH) (B1617,B1618)

Lexus NX Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Front Airbag Sensor Lost Communication (LH) (B1617,B1618)

DESCRIPTION

The front airbag sensor LH circuit consists of the airbag ECU assembly and front airbag sensor LH.

The front airbag sensor LH detects impacts to the vehicle and sends signals to the airbag ECU assembly to determine if the airbag should be deployed.

DTC B1617 or B1618 is stored when a malfunction is detected in the front airbag sensor LH circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1617

Front Airbag Sensor Lost Communication (LH)

One of the following conditions is met:

  • The airbag ECU assembly detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the front airbag sensor LH circuit for 2 seconds.
  • A front airbag sensor LH malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Engine room main wire
  • Front airbag sensor LH
  • Airbag ECU assembly

B1618

Front Airbag Sensor Initialization Error (LH)

One of the following conditions is met:

  • The airbag ECU assembly detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the front airbag sensor LH circuit for 2 seconds.
  • A front airbag sensor LH malfunction.
  • An airbag ECU assembly malfunction.
  • Instrument panel wire
  • Engine room main wire
  • Front airbag sensor LH
  • 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

PROCEDURE

1.

CHECK CONNECTION OF CONNECTORS

(a) Turn the power switch off.

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

(c) Check that the connectors are properly connected to the airbag ECU assembly and front airbag sensor LH.

The connectors are not properly connected

CONNECT CONNECTORS PROPERLY

The connectors are properly connected

2.

CHECK CONNECTORS

(a) Disconnect the connectors from the airbag ECU assembly and front airbag sensor LH.

(b) Check that the connectors (on the airbag ECU assembly side and front airbag sensor LH side) are not damaged.

*1

Front Airbag Sensor LH

*2

Airbag ECU Assembly

*3

Engine Room Main Wire

*4

Instrument Panel Wire

The connectors are deformed or damaged

REPLACE INSTRUMENT PANEL WIRE OR ENGINE ROOM MAIN WIRE

The connectors are not deformed or damaged

3.

CHECK FRONT AIRBAG SENSOR LH CIRCUIT

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

*1

Front Airbag Sensor LH

*2

Airbag ECU Assembly

*3

Connector E

*4

Connector B

*5

Service Wire

-

-

*a

Rear view of wire harness connector

(to Front Airbag Sensor LH)

*b

Rear view of wire harness connector

(to Airbag ECU 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

A14-2 (+SL) - Body ground

Power switch on (IG)

Below 1 V

A14-1 (-SL) - 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) Using a service wire, connect terminals 30 (+SL) and 28 (-SL) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A14-2 (+SL) - A14-1 (-SL)

Always

Below 1 Ω

(h) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A14-2 (+SL) - A14-1 (-SL)

Always

1 MΩ or higher

A14-2 (+SL) - Body ground

Always

1 MΩ or higher

A14-1 (-SL) - Body ground

Always

1 MΩ or higher

NG

GO TO STEP 5

OK

4.

CHECK FRONT AIRBAG SENSOR LH

(a) Connect the connectors to the airbag ECU assembly.

*1

Front Airbag Sensor RH

*2

Airbag ECU Assembly

(b) Interchange the front airbag sensor LH with RH and connect the connectors to them.

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

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

(e) Clear the DTCs stored in memory.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the power switch off.

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

(h) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

Codes other than DTC B1612, B1613, B1617 and B1618 may be output at this time, but they are not related to this check.

(i) Turn the power switch off.

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

(k) Return the front airbag sensor RH and LH to their original positions and connect the connectors to them.

DTC B1617 or B1618 is output

REPLACE AIRBAG ECU ASSEMBLY

DTC B1612 or B1613 is output

REPLACE FRONT AIRBAG SENSOR LH

DTC B1612, B1613, B1617 and B1618 are not output

USE SIMULATION METHOD TO CHECK

5.

CHECK INSTRUMENT PANEL WIRE

(a) Disconnect the instrument panel wire connector from the engine room main wire.

*1

Front Airbag Sensor LH

*2

Airbag ECU Assembly

*3

Engine Room Main Wire

*4

Instrument Panel Wire

*5

Connector C

*6

Connector B

*7

Service Wire

-

-

*a

Front view of wire harness connector

(to Engine Room Main Wire)

*b

Rear view of wire harness connector

(to 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).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

AI10-1 (+SL) - Body ground

Power switch on (IG)

Below 1 V

AI10-2 (-SL) - 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) Using a service wire, connect terminals 30 (+SL) and 28 (-SL) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

AI10-1 (+SL) - AI10-2 (-SL)

Always

Below 1 Ω

(i) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

AI10-1 (+SL) - AI10-2 (-SL)

Always

1 MΩ or higher

AI10-1 (+SL) - Body ground

Always

1 MΩ or higher

AI10-2 (-SL) - Body ground

Always

1 MΩ or higher

OK

REPLACE ENGINE ROOM MAIN WIRE

NG

REPLACE INSTRUMENT PANEL WIRE

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