Mitsubishi Montero Sport (2004+). Manual - part 571

THEFT ALARM

TSB Revision

CHASSIS ELECTRICAL

54-271

STEP 7. Check the input signal (by using pulse check).

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Inspect the following inputs.

• Key reminder switch

• Driver's and passenger's door switch

• Driver's and passenger's door lock key cylinder switch

• Driver's and passenger's door lock actuator switch

• Liftgate switch

• Gate lock key cylinder switch

Q: Does the tone alarm of scan tool MB991958 sound when 

the input signal enters?
YES : Replace the ETACS-ECU. Check that the 

malfunctions eliminated.

NO :  Check the faulty input circuit. Refer to Inspection 

Procedure 8 

P.54-302

.

STEP 8. Check the input signal (by using a voltmeter).

Check the input signals from the following switches:
(1) Use special tool MB991529 to connect a voltmeter between 

ground terminal 4 or 5 and ETACS-ECU terminal 9 of the 

data link connector.

(2) Check that the voltmeter indicator deflects once when the 

input signal.

• Key reminder switch

• Driver's and passenger's door switch

• Driver's and passenger's door lock key cylinder switch

• Driver's and passenger's door lock actuator switch

• Liftgate switch

• Gate lock key cylinder switch

Q: Does the voltmeter indicator deflect?

YES : Replace the ETACS-ECU. Check that the 

malfunctions eliminated.

NO :  Check the faulty input circuit. Refer to Symptom Chart 

8 

P.54-302

.

AK303629AB

MB991911

MB991827

MB991824 

16-PIN

AC003527

GROUNDED TERMINAL

ETACS-ECU 
TERMINAL

MB991529

AB

THEFT ALARM

TSB Revision

CHASSIS ELECTRICAL

54-272

INSPECTION PROCEDURE 2: Horn does not Sound when the Theft-alarm is Triggered.

JUNCTION 
BLOCK

THEFT-ALARM
HORN RELAY

THEFT-ALARM
HORN

DIODE

ETACS-
ECU

FUSIBLE
LINK

8

Theft-Alarm Horn Drive Circuit

AC003828AC

CONNECTOR: A-91

A-91(B)

AC003830

CONNECTOR: C-85

AG

C-85 (B)

THEFT ALARM

TSB Revision

CHASSIS ELECTRICAL

54-273

.

CIRCUIT OPERATION
The ETACS-ECU will sound the theft-alarm horn and 
horn if the theft-alarm system or the keyless entry 
system answerback is triggered.

.

TECHNICAL DESCRIPTION (COMMENT)
The theft-alarm horn is shared by the keyless entry 
system. If the theft-alarm horn sounds normally 
through the keyless entry system answerback, the 
ETACS-ECU may be defective.

.

TROUBLESHOOTING HINTS

• Malfunction of the theft-alarm horn

• Malfunction of the theft-alarm horn relay

• Malfunction of the ETACS-ECU

• Damaged harness wires or connectors

.

AC003824

AC

CONNECTOR: C-100

C-100

AC003432

CONNECTOR: D-02

JUNCTION BLOCK (FRONT)

AF

D-02 (GR)

AC003444

AE

CONNECTOR: D-13

JUNCTION BLOCK (REAR)

D-13

AC003524

CONNECTOR: D-26

AC

JUNCTION BLOCK (REAR)

D-26 (B)

THEFT ALARM

TSB Revision

CHASSIS ELECTRICAL

54-274

DIAGNOSIS

Required Special Tool:

• MB991223: Test Harness Set 

STEP 1. Check the keyless entry system horn answerback.

Activate the keyless entry system horn answerback. (Refer to 
GROUP 42, Keyless Entry System 

− On-vehicle Service − 

Enabling/disabling the Answerback Function.)
Q: Does the horn answerback function work?

YES : Replace the ETACS-ECU. The theft-alarm horn 

should sound when the theft-alarm system is 
triggered.

NO :  Go to Step 2.

STEP 2. Check the theft-alarm horn.

Connect the battery as shown and check that the theft-alarm 
horn sounds.
Q: Is the theft-alarm horn in good condition?

YES : Go to Step 3.
NO :  Replace it. The theft-alarm horn should sound when 

the theft-alarm system is triggered.

STEP 3. Check the theft-alarm horn relay.

Follow the table below to check the theft-alarm horn relay oper-
ation.

Q: Is the theft-alarm horn relay in good condition?

YES : Go to Step 4.
NO :  Replace it. The theft-alarm horn should sound when 

the theft-alarm system is triggered.

ACX02352

BATTERY 
VOLTAGE

TESTER 
CONNECTION

SPECIFIED 
CONDITION

Not applied

1 

− 3 

Open circuit

Supplied

• Connect terminal 

2 to the positive 
battery terminal

• Connect terminal 

4 to the negative 
battery terminal

1 

− 3 

Less than 2 ohms

AC002838 AB

THEFT-ALARM HORN RELAY