Mitsubishi Lancer (4A9 engine). Manual - part 236
SECURITY ALARM
CHASSIS ELECTRICAL
54A-606
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 ETACS-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 ETACS-ECU may be defective
• The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals 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 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?
YES :
Go to Step 2
NO :
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?
YES :
Diagnose the ETACS-ECU. Refer to
GROUP 54A, Diagnosis .
NO :
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?
YES :
Go to Step 4.
NO :
Replace LIN cutoff control unit.
STEP 4. Connector check: C-301 ETACS-ECU
connector, C-312 ETACS-ECU connector, C-63
LIN cutoff control unit connector
Q: Is the check result normal?
YES :
Go to Step 5.
NO :
Repair the defective connector.
STEP 5. Wiring harness check between the C-301
ETACS-ECU connector terminal No. 13 and C-63
LIN cutoff control unit connector terminal No. 3
Check the signal line for open circuit and short cir-
cuit.
Q: Is the check result normal?
YES :
Go to Step 6.
NO :
Repair the wiring harness.
STEP 6. Wiring harness check between the C-312
ETACS-ECU connector terminal No. 9 and C-63
LIN cutoff control unit connector terminal No. 8
Check the signal line for short circuit.
NOTE: Prior to the wiring harness inspection, check
C-127 intermediate connector, and repair if neces-
sary.
Q: Is the check result normal?
YES :
Go to Step 7.
NO :
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?
YES :
The trouble can be an intermittent
malfunction (Refer to GROUP 00
− How to
Cope with Intermittent Malfunction ).
NO :
Replace the ETACS-ECU.