Horn Circuit
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
CHECK HORN OPERATION
(a) Press the horn switch and check if the horn(s) sound.
OK:
Horn(s) operate normally.
| NG | .gif) | GO TO HORN SYSTEM |
|
.gif)
PERFORM ACTIVE TEST USING TECHSTREAM (VEHICLE HORN)
(a) Operate the Techstream according to the steps on the display and select Active Test (See page .gif)
).
Main Body
Tester Display | Test Part | Control Range | Diagnostic Note |
|---|---|---|---|
Vehicle Horn |
Vehicle horn(s) |
ON/OFF |
- |
OK:
Horn(s) operate normally.
| OK | | PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
|
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 ).
(c) Measure the resistance according to the value(s) in the table below.
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 |
| OK | | REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
Test yourself
A quick Toyota 4Runner quiz: every answer comes with an explanation and a link to the manual page.