Inspection Procedure 6: The activated security alarm siren sounds even though no faulty operation is made. <Vehicles with security alarm sensor>



caution
  • Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
  • When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID .)


COMMENTS ON TROUBLE SYMPTOM


If the activated security alarm siren sounds even though no faulty operation is made, the security alarm siren may not be able to receive the signal from the ETACS-ECU.
note The security alarm siren may be sounding by false alarm. Investigate what kind of situation the security alarm siren sounded under. Check if there was any condition that caused false alarm.

PROBABLE CAUSES




DIAGNOSIS PROCEDURE


STEP 1. Vehicle status check when security alarm siren is sounding


(1)Since it is suspected that the security alarm has sounded accidentally, investigate whether the vehicle is under the situation below. Repair if an abnormality is found.

  • The windows and sunroof are open.
  • Some moving accessories are fitted in the vehicle.
  • The interior equipment has been modified before a malfunction occurs.
(2)Set the sensitivity level of security alarm sensor to Level 4 by using the customisation function.
(3)Check if the security alarm siren sounds during the status of "Ready to be triggered" even though no faulty operation is made.

Q. Is the check result normal?

Go to Step 2
The diagnosis is complete.

STEP 2. M.U.T.-III diagnosis code.


Check if diagnosis code is set to the ETACS-ECU.

Q. Is the diagnosis code set?

Diagnose the ETACS-ECU. Refer to GROUP 54A, Diagnosis .
Go to Step 3

STEP 3. Check of open circuit in BUP4 line between the ETACS-ECU connector and security alarm siren connector.


Q. Is the check result normal?

Go to Step 4
Repair the connector(s) or wiring harness.

STEP 4. Check of open circuit in (LITI) line between security alarm siren connector and ETACS-ECU connector.


Q. Is the check result normal?

Go to Step 5
Repair the connector(s) or wiring harness.

STEP 5. Retest the security alarm system.


Check if the activated security alarm siren sounds even though no faulty operation is made.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the ETACS-ECU.