Security 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 security horn assembly to sound
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
PROCEDUREPERFORM ACTIVE TEST USING TECHSTREAM (SECURITY 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 |
|---|---|---|---|
Security Horn |
Security horn |
ON/OFF |
- |
OK:
Security horn operates normally.
| OK | .gif) | PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
|
.gif)
INSPECT S-HORN RELAY
(a) Remove the S-HORN relay from the engine room relay block. |
 |
(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 not applied to terminals 1 and 2 |
10 kΩ or higher |
3 - 5 |
Battery voltage is applied to terminals 1 and 2 |
Below 1 Ω |
| NG | | REPLACE S-HORN RELAY |
|
INSPECT SECURITY HORN ASSEMBLY
(a) Remove the security horn (See page ).
(b) Apply battery voltage to the horn connector and check the operation of the horn.
OK:
Measurement Condition | Specified Condition |
|---|---|
Battery positive (+) → Terminal 1 Battery negative (-) → Horn bracket |
Horn sounds |
| NG | | REPLACE SECURITY HORN ASSEMBLY |
|
CHECK HARNESS AND CONNECTOR (ENGINE ROOM RELAY BLOCK - MAIN BODY ECU, SECURITY HORN AND BATTERY)
(a) Remove the S-HORN relay from the engine room relay block.
(b) Remove the main body ECU (See page ).
(c) Disconnect the A32 horn connector.
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection | Condition | Specified Condition |
|---|---|---|
Relay block S-HORN relay terminal 1 - A-17 (SH) |
Always |
Below 1 Ω |
Relay block S-HORN relay terminal 3 - A32-1 |
Always |
Below 1 Ω |
A-17 (SH) - Body ground |
Always |
10 kΩ or higher |
A32-1 - Body ground |
Always |
10 kΩ or higher |
(e) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection | Condition | Specified Condition |
|---|---|---|
Relay block S-HORN relay terminal 2 - Body ground |
Always |
11 to 14 V |
Relay block S-HORN relay terminal 5 - Body ground |
Always |
11 to 14 V |
| 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.