Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Theft Warning Siren Circuit

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Theft Deterrent System / Theft Warning Siren Circuit

DESCRIPTION

The theft warning siren assembly sounds if either of the following conditions is met:

  • The theft deterrent system is in the alarm sounding state.
  • The theft warning siren assembly is in the armed state when the power source, ground or communication line is open.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Before replacing the main body ECU (multiplex network body ECU), refer to Registration.

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (SECURITY HORN2)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

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

(e) Perform the Active Test according to the display on the Techstream.

Body Electrical > Main Body > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

Security Horn2

Theft warning siren assembly

OFF/ON

-
Body Electrical > Main Body > Active Test

Tester Display

Security Horn2

OK:

The theft warning siren assembly sounds and stops correctly when operated using the Techstream.

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

2.

CHECK HARNESS AND CONNECTOR (BATTERY - THEFT WARNING SIREN ASSEMBLY - BODY GROUND)

(a) Disconnect the R28 theft warning siren assembly connector.

*a

Front view of wire harness connector

(to Theft Warning Siren Assembly)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

R28-1 (+B) - Body ground

Always

11 to 14 V

Standard Resistance:

Tester Connection

Condition

Specified Condition

R28-3 (GND) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

3.

CHECK HARNESS AND CONNECTOR (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) - THEFT WARNING SIREN ASSEMBLY)

(a) Disconnect the J9 main body ECU (multiplex network body ECU) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J9-18 (SSCL) - R28-2 (CONT)

Always

Below 1 Ω

J9-18 (SSCL) or R28-2 (CONT) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

REPLACE THEFT WARNING SIREN ASSEMBLY

(a) Temporarily replace the theft warning siren assembly with a new or known good one.

Click here

NEXT

5.

CHECK THEFT WARNING SIREN ASSEMBLY

(a) Turn the engine switch on (IG), then off.

(b) Set the theft deterrent system to "ARMED STATE".

Click here

(c) Check that the security indicator changes from illuminated to blinking.

(d) Change the theft deterrent system to "ALARM SOUNDING STATE".

Click here

(e) Check that the theft warning siren assembly is sounding.

OK:

Theft warning siren assembly is sounding.

OK

END (THEFT WARNING SIREN ASSEMBLY WAS DEFECTIVE)
NG

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

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