Inspection Procedure 4: The activated security alarm siren sounds even though no faulty operation is made.
caution
Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
TECHNICAL DESCRIPTION (COMMENT)
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 CAN converter-ECU via the LIN cutoff control unit.
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.
TROUBLESHOOTING HINTS
security alarm siren may be defective
LIN cutoff control unit may be defective
The CAN converter-ECU may be defective
The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
DIAGNOSIS PROCEDURE
STEP 1. Vehicle status check when security alarm siren is sounding
(1)Since it is suspected that the security alarm siren 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 siren to 70% 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 CAN converter-ECU.
Q.
Is the diagnosis code set?
Diagnose the CAN converter-ECU. Refer to GROUP 54A, Diagnosis .
Go to Step 3.
STEP 3. LIN cutoff control unit check
Check the continuity of the LIN cutoff control unit. (Refer to .)
Q.
Is the check result normal?
Go to Step 4.
Replace LIN cutoff control unit.
STEP 4. Connector check: D-252 CAN converter-ECU connector, D-41 LIN cutoff control unit connector
Q.
Is the check result normal?
Go to Step 5.
Repair the defective connector.
STEP 5. Wiring harness check between the D-252 CAN converter-ECU connector terminal No. 13 and D-41 LIN cutoff control unit connector terminal No. 3
Check the signal line for open circuit and short circuit.
Q.
Is the check result normal?
Go to Step 6.
Repair the wiring harness.
STEP 6. Wiring harness check between the D-252 CAN converter-ECU connector terminal No. 5 and D-41 LIN cutoff control unit connector terminal No. 8
Check the signal line for short circuit.
Q.
Is the check result normal?
Go to Step 7.
Repair the wiring harness.
STEP 7. 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 Cope with Intermittent Malfunction ).
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Go to Step 2
The diagnosis is complete.
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