Lexus NX: Security Horn Circuit

DESCRIPTION

When the theft deterrent system is switched from the armed state to the alarm sounding state, the main body ECU (multiplex network body ECU) transmits a signal to cause the security horn to sound at intervals of 0.4 seconds.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.

    Click here

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (SECURITY HORN)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Main Body / Active Test.

(e) According to the display on the Techstream, perform the Active Test.

Body Electrical > Main Body > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

Security Horn

Security horn assembly

ON or OFF

-

Body Electrical > Main Body > Active Test

Tester Display

Security Horn

OK:

The security horn assembly sounds and stops correctly when operated through the Techstream.

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

2.

INSPECT SECURITY HORN ASSEMBLY

(a) Remove the security horn assembly.

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(b) Inspect the security horn assembly.

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NG

REPLACE SECURITY HORN ASSEMBLY

OK

3.

INSPECT SECURITY WARNING RELAY (S-HORN RELAY)

(a) Remove the security warning relay (S-HORN relay).

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

Battery voltage is applied between terminals 2 - 1

Below 1 Ω

3 - 5

Battery voltage is not applied between terminals 2 - 1

10 kΩ or higher

NG

REPLACE SECURITY WARNING RELAY (S-HORN RELAY)

OK

4.

CHECK HARNESS AND CONNECTOR (SECURITY WARNING RELAY [S-HORN RELAY] - MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU])

(a) Remove the main body ECU (multiplex network body ECU).

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(b) Connect the instrument panel junction block assembly connectors.

(c) Remove the security warning relay (S-HORN relay).

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 - A-29 (SH)

Always

Below 1 Ω

2 - Body ground

Always

10 kΩ or higher

A-29 (SH) - Body ground

Always

10 kΩ or higher

NG

GO TO STEP 7

OK

5.

CHECK HARNESS AND CONNECTOR (BATTERY - SECURITY WARNING RELAY [S-HORN RELAY])

(a) Remove the security warning relay (S-HORN relay).

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

1 - Body ground

Power switch off

11 to 14 V

5 - Body ground

Power switch off

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

6.

CHECK HARNESS AND CONNECTOR (SECURITY WARNING RELAY [S-HORN RELAY] - SECURITY HORN ASSEMBLY AND BODY GROUND)

(a) Remove the security warning relay (S-HORN relay).

(b) Disconnect the A10 security horn assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - A10-1

Always

Below 1 Ω

A10-2 - Body ground

Always

Below 1 Ω

3 - Body ground

Always

10 kΩ or higher

A10-1 - Body ground

Always

10 kΩ or higher

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

7.

CHECK HARNESS AND CONNECTOR (SECURITY HORN RELAY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the 4B instrument panel junction block assembly connector.

(b) Remove the security warning relay (S-HORN relay).

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 - 4B-48

Always

Below 1 Ω

2 - Body ground

Always

10 kΩ or higher

4B-48 - Body ground

Always

10 kΩ or higher

OK

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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