Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: 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 horns to sound at intervals of 0.4 seconds.

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.

INSPECT HORNS

(a) Press the horn switch and check if the horns sound.

Result

Proceed to

Horns sound

A

Horns do not sound

B

B

GO TO HORN SYSTEM

A

2.

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

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

Click here

*a

Component without harness connected

(Instrument Panel Junction Block Assembly)

-

-

(b) Disconnect the 2C instrument panel junction block assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2C-27 - MB-28 (HORN)

Always

Below 1 Ω

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

    Engine Hood Courtesy Switch Circuit
    DESCRIPTION The engine hood courtesy switch is built into the hood lock assembly. This switch turns on when the engine hood is closed and turns off when the engine hood is opened. WIRING DIAGRAM CAUT ...

    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 a ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Sfi System: Brake Switch "B" Circuit Short to Battery (P070312)
    DESCRIPTION The stop light switch assembly is part of a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. This DTC indicates that the stop light switch assembly is remaining on. When the stop ...

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Camshaft Oil Control Solenoid (for Bank 2): Installation
    INSTALLATION PROCEDURE 1. INSTALL CAMSHAFT TIMING OIL CONTROL SOLENOID ASSEMBLY (for Intake Side of Bank 2) (a) Apply engine oil to a new O-ring and install it to the camshaft timing oil control solenoid assembly as shown in the illustration. NOTICE: Do not damage the O-ring. *1 O- ...

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

    © 2026 Copyright www.lexusrx.net
    0.0137