Mitsubishi Montero (2002-2004). Manual - part 359

SYMPTOM PROCEDURES

TSB Revision

SWS SYMPTOM PROCEDURES

54Bb-483

 STEP 10. Check the input signal (by using the pulse check 
mode of the monitor.)
Check the input signals from the following switches:

• Key reminder switch

• Driver’s, front passenger’s, rear and back door lock actuator 

switch

• Driver’s, front passenger’s and back door lock key cylinder 

switch

• Food switch

Operate scan tool MB991502 according to the procedure below 
to display "PULSE CHECK."

1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "PULSE CHECK."

Check if scan tool MB991502 sounds or not.

Q:  When the key reminder switch, driver’s, front 

passenger’s, rear and back door lock actuator switches, 
driver’s, front passenger’s and back door look key 
cylinder switches, hood switch are operated, does scan 
tool MB991502 sound in all cases?
YES : Replace the ETACS-ECU. The theft-alarm indicator 

light should illuminate, and the theft-alarm system 
should be set normally.

NO : 

• Scan tool MB991502 does not sound when the 

key reminder switch is operated: Refer to 
Inspection Procedure P-1 "ETACS-ECU does not 
receive any signal from the key reminder switch 

P.54Bc-49

."

• Scan tool MB991502 does not sound when the 

driver's, the front passenger's, the rear and the 
back door lock actuator switches are operated: 
Refer to Inspection Procedure P-6 "ETACS-ECU 
does not receive signals from the driver's or the 
front passenger's door lock actuator switches 

P.54Bc-93

."

• Scan tool MB991502 does not sound when the 

driver's, the front passenger's and the back door 
lock key cylinder switches are operated: Refer to 
Inspection Procedure P-5 "ETACS-ECU does not 

ITEM NAME

CONDITION

Key reminder switch

Remove and reinsert the 
ignition key

Driver's, front passenger's, 
rear and back door lock 
actuator switches

Lock or unlock each door 

Driver's, front passenger's, 
and back door lock key 
cylinder switches

Operate the door lock key 
cylinder at each door

Hood switch

Open and close the hood

AC204222AB

16-pin

13-pin

MB991502

MB991862

SYMPTOM PROCEDURES

TSB Revision

SWS SYMPTOM PROCEDURES

54Bb-484

receive signals from the driver's and the front 
passenger's door lock key cylinder switches 

P.54Bc-75

."

• Scan tool MB991502 does not sound when the 

hood switch is operated: Refer to Inspection 
Procedure P-9 "ETACS-ECU does not receive any 
signal from the hood switch 

P.54Bc-140

."

INSPECTION PROCEDURE N-2: Theft-alarm System: Horn does not sound when the theft-alarm is 
triggered.

Horn and Theft-alarm Horn Drive Circuit

SYMPTOM PROCEDURES

TSB Revision

SWS SYMPTOM PROCEDURES

54Bb-485

.

CIRCUIT OPERATION
When the theft-alarm system is triggered, the 
ETACS-ECU sounds the theft-alarm horn and all the 
vehicle horns.

.

TECHNICAL DESCRIPTION (COMMENT)
If the theft-alarm horn and the vehicle horns do not 
sound when the theft-alarm system is triggered, the 
ETACS-ECU may be defective.

.

TROUBLESHOOTING HINTS

• The theft-alarm horn may be defective

• The horn may be defective

• The theft-alarm horn relay may be defective

• The horn relay 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

AC204167

CONNECTORS : A-04, A-17

A-17

AS

A-04(B)

AC204183

CONNECTORS : A-10X, A-11X

A-11X

A-10X

AK

AC204166

CONNECTORS : A-27, A-28

AJ

A-28(B)

A-27(B)

AC204170

CONNECTORS : D-27, D-28

BQ

D-28

D-27

AC204174

CONNECTOR : D-223

D-223(B)

AF

SYMPTOM PROCEDURES

TSB Revision

SWS SYMPTOM PROCEDURES

54Bb-486

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check which horn is defective.
Check which horn does not sound when the theft-alarm system 
is triggered.
Q: Which horn does not sound?

theft-alarm horn : Go to Step 2.
horns (high and low)  : Go to Step 12.
horn (high or low)  : Go to Step 20.
theft-alarm horn and all vehicle horns : Replace the 

ETACS-ECU. All the vehicle horn (including the theft-
alarm horn) should sound when the theft-alarm 
system is triggered.

STEP 2. Check the theft-alarm horn.
Connect the battery as shown, and check that the theft-alarm 
horn sounds.
Q: Does the theft-alarm horn sound?

YES : Go to Step 3.
NO :  Replace the theft-alarm horn. All the vehicle horn 

(including the theft-alarm horn) should sound when 
the theft-alarm system is triggered.

STEP 3. Check the theft-alarm horn relay.

Q: Is the theft-alarm horn relay normal?

YES : Go to Step 4.
NO :  Replace the theft-alarm horn relay. All the vehicle 

horn (including the theft-alarm horn) should sound 
when the theft-alarm system is triggered.

ACX02352

BATTERY 
VOLTAGE

TESTER 
CONNECTION

SPECIFIED 
CONDITION

Not applied

4 

− 5

Open circuit

1 

− Battery (−) 

terminal,
3 

− Battery (+) 

terminal

4 

− 5

Less than 2 ohms

1

2 3

4

5

1

3

4

5

AC204637

RELAY SIDE

AB

THEFT-ALARM HORN RELAY