Toyota 4Runner: Horn Circuit

Toyota 4Runner Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Theft Deterrent System / Horn Circuit

DESCRIPTION

When the theft deterrent system is in the alarm sounding state, the main body ECU outputs a signal repeatedly at 0.4 second intervals, causing the horn(s) to sound.

WIRING DIAGRAM

PROCEDURE

1.	CHECK HORN OPERATION

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

OK:

Horn(s) operate normally.

GO TO HORN SYSTEM

2.	PERFORM ACTIVE TEST USING TECHSTREAM (VEHICLE HORN)

(a) Operate the Techstream according to the steps on the display and select Active Test (See page ).

Main Body

Tester Display	Test Part	Control Range	Diagnostic Note
Vehicle Horn	Vehicle horn(s)	ON/OFF	-

OK:

Horn(s) operate normally.

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

3.	CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - MAIN BODY ECU)

(a) Disconnect the 1C relay connector.

(b) Remove the main body ECU (See page ).

Standard Resistance:

Tester Connection	Condition	Specified Condition
1C-7 - A-28 (HORN)	Always	Below 1 Ω
1C-7 or A-28 (HORN) - Body ground	Always	10 kΩ or higher

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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