Lexus NX: 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 to sound at intervals of 0.4 seconds.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
- Inspect the fuses for circuits related to this system before performing the following procedure.
-
If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.
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PROCEDURE
| 1. | PERFORM ACTIVE TEST USING TECHSTREAM (SECURITY HORN) |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Body Electrical / Main Body / Active Test.
(e) According to the display on the Techstream, perform the Active Test.
Body Electrical > Main Body > Active Test| Tester Display | Measurement Item | Control Range | Diagnostic Note |
|---|---|---|---|
| Security Horn | Security horn assembly | ON or OFF | - |
| Tester Display |
|---|
| Security Horn |
OK:
The security horn assembly sounds and stops correctly when operated through the Techstream.
| OK | .gif) | REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) |
|
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| 2. | INSPECT SECURITY HORN ASSEMBLY |
(a) Remove the security horn assembly.
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(b) Inspect the security horn assembly.
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| NG | | REPLACE SECURITY HORN ASSEMBLY |
|
| 3. | INSPECT SECURITY WARNING RELAY (S-HORN RELAY) |
| (a) Remove the security warning relay (S-HORN relay). |
|
(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 applied between terminals 2 - 1 | Below 1 Ω |
| 3 - 5 | Battery voltage is not applied between terminals 2 - 1 | 10 kΩ or higher |
| NG | | REPLACE SECURITY WARNING RELAY (S-HORN RELAY) |
|
| 4. | CHECK HARNESS AND CONNECTOR (SECURITY WARNING RELAY [S-HORN RELAY] - MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU]) |
(a) Remove the main body ECU (multiplex network body ECU).
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(b) Connect the instrument panel junction block assembly connectors.
(c) Remove the security warning relay (S-HORN relay).
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 2 - A-29 (SH) | Always | Below 1 Ω |
| 2 - Body ground | Always | 10 kΩ or higher |
| A-29 (SH) - Body ground | Always | 10 kΩ or higher |
| NG | | GO TO STEP 7 |
|
| 5. | CHECK HARNESS AND CONNECTOR (BATTERY - SECURITY WARNING RELAY [S-HORN RELAY]) |
| (a) Remove the security warning relay (S-HORN relay). |
|
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Switch Condition | Specified Condition |
|---|---|---|
| 1 - Body ground | Power switch off | 11 to 14 V |
| 5 - Body ground | Power switch off | 11 to 14 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 6. | CHECK HARNESS AND CONNECTOR (SECURITY WARNING RELAY [S-HORN RELAY] - SECURITY HORN ASSEMBLY AND BODY GROUND) |
(a) Remove the security warning relay (S-HORN relay).
(b) Disconnect the A10 security horn assembly connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 3 - A10-1 | Always | Below 1 Ω |
| A10-2 - Body ground | Always | Below 1 Ω |
| 3 - Body ground | Always | 10 kΩ or higher |
| A10-1 - Body ground | Always | 10 kΩ or higher |
| OK | | REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
| 7. | CHECK HARNESS AND CONNECTOR (SECURITY HORN RELAY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) |
(a) Disconnect the 4B instrument panel junction block assembly connector.
(b) Remove the security warning relay (S-HORN relay).
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 2 - 4B-48 | Always | Below 1 Ω |
| 2 - Body ground | Always | 10 kΩ or higher |
| 4B-48 - Body ground | Always | 10 kΩ or higher |
| OK | | REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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