Lexus NX: SRS Warning Light Remains ON

DESCRIPTION

The SRS warning light is located in the combination meter assembly.

When the SRS is normal, the SRS warning light comes on for approximately 6 seconds after the power switch is turned from off on (IG), and then goes off automatically.

If there is a malfunction in the SRS, the SRS warning light comes on to inform the driver of a problem.

If a malfunction occurs in the airbag ECU assembly, combination meter assembly or wire harness connected to the airbag ECU assembly or combination meter assembly, the SRS warning light comes on.

The SRS is equipped with a voltage-increase circuit (DC-DC converter) in the airbag ECU assembly in case the source voltage drops.

When the auxiliary battery voltage drops, the voltage-increase circuit (DC-DC converter) functions to increase the voltage of the SRS to normal voltage.

A malfunction in this circuit is not recorded in the airbag ECU assembly. The SRS warning light automatically goes off when the source voltage returns to normal.

The signal to illuminate the SRS warning light is transmitted from the airbag ECU assembly to the combination meter assembly through the CAN communication system.

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

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.
  • When replacing the combination meter assembly, make sure to replace it with a new one.

PROCEDURE

1.

CHECK CAN COMMUNICATION SYSTEM

(a) Check if a CAN communication DTC is output.

Click here

DTCs are output

GO TO CAN COMMUNICATION SYSTEM

DTC is not output

2.

CHECK AUXILIARY BATTERY

(a) Measure the auxiliary battery voltage with the power switch off.

Standard voltage:

11 to 14 V

HINT:

It may be possible to tell whether the auxiliary battery is discharged by operating the horn.

If the voltage is below 11 V, recharge or replace the auxiliary battery before proceeding to the next step.

NG

REPLACE OR RECHARGE AUXILIARY BATTERY

OK

3.

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 combination meter assembly.

The connectors are not properly connected

CONNECT CONNECTORS PROPERLY

The connectors are properly connected

4.

CHECK HARNESS AND CONNECTOR (AIRBAG ECU ASSEMBLY - BATTERY AND BODY GROUND)

(a) Disconnect the connectors from the airbag ECU assembly.

*a

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) Operate all the components of the electrical system (defogger, wipers, headlights, heater blower, etc.).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

I58-21 (IG2) - Body ground

Power switch on (IG)

11 to 14 V

I58-21 (IG2) - Body ground

Power switch off

Below 1 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I58-25 (E1) - Body ground

Always

Below 1 Ω

I58-26 (E2) - Body ground

Always

Below 1 Ω

NG

REPLACE HARNESS AND CONNECTOR

OK

5.

CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BATTERY AND BODY GROUND)

(a) Turn the power switch off.

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

*a

Front view of wire harness connector

(to Combination Meter Assembly)

(c) Disconnect the connector from the combination meter assembly.

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

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

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

I10-21 (IG+) - Body ground

Power switch on (IG)

11 to 14 V

I10-22 (B) - Body ground

Power switch off

11 to 14 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I10-40 (EP) - Body ground

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

6.

CHECK SRS WARNING LIGHT (SHORT TO GROUND)

(a) Turn the power switch off.

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

(c) Connect the connector to the combination meter assembly.

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

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

(f) Check the SRS warning light condition.

OK:

After the primary check period, the SRS warning light goes off for approximately 10 seconds and then remains on.

HINT:

The primary check period is approximately 6 seconds after the power switch is turned on (IG).

OK

REPLACE AIRBAG ECU ASSEMBLY

NG

GO TO METER / GAUGE SYSTEM

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