Mitsubishi Montero (2004+). Manual - part 787

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-405

.

CIRCUIT OPERATION

• The ETACS-ECU sends a fog light illumination 

request signal ("LIGHT ON" signal) to the 
front-ECU when the fog light switch is turned on 
while the headlights are on.

• Then the front-ECU switches on its relay to illumi-

nate the fog lights.

.

TECHNICAL DESCRIPTION (COMMENT)
If the headlights illuminate normally, the fog light 
relay, the fog light switch, the front-ECU or the 
ETACS-ECU may be defective.

.

TROUBLESHOOTING HINTS

• The fog light relay may be defective

• The fog light switch may be defective

• The front-ECU 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

Required Special Tools:

• MB991223: Harness Set

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

• MB991813: SWS Monitor Kit

• MB991806: SWS Monitor Cartridge

• MB991812: SWS Monitor Harness (For Column-ECU)

• MB991822: Probe Harness

STEP 1. Verify the headlight operation.
Q: Do the headlights illuminate normally?

The lights illuminate normally at both high and low 
beams : Go to Step 2.
Headlights do not Illuminate at low beam : Refer to 

Inspection Procedure J-2 "Headlights (low-beam) do 
not illuminate normally 

P.54B-304

."

Headlights do not Illuminate at high beam : Refer to 

Inspection Procedure J-3 "Headlights (high-beam) do 
not illuminate normally 

P.54B-308

."

AC204183

CONNECTORS : A-07X, A-13X

A-13X

A-07X

AJ

AC204167

CONNECTORS : A-15, A-21, A-25

A-15

AQ

A-25(B)

A-21(B)

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-406

STEP 2. Check the input signal by using "FUNCTION 
DIAG." menu of the SWS monitor.
Set each switch to the following condition before checking input 
signal from the fog light switch:

• Ignition switch: ON

• Fog light switch: ON

NOTE: Turn the ignition switch to the "ON" position in order to 
disable the headlight automatic shutdown function.

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 the special tool. Refer to "How to connect SWS 

monitor 

P.54B-7

.

(2) Operate scan tool MB991958 according to the procedure 

below to display "F.FOG LIGHT"

1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "FUNCTION DIAG."
5. Select "LIGHTING."
6. Select "F.FOG LIGHT."

(3) Check that normal conditions are displayed on the items 

described in the table below.

Q: Are normal conditions displayed on the "IG SW(IG1)" 

and "F.FOG LIGHT"?
Normal conditions are displayed for all the items : Go to 

Step 3.

Normal condition is not displayed on the "IG SW(IG1)" : 

Refer to Inspection Procedure O-2 "ETACS-ECU 
does not receive any signal from the ignition switch 
(IG1) 

P.54B-505

."

Normal condition is not displayed on the "F.FOG LIGHT" 
: 

Refer to Inspection Procedure O-3 "ETACS-ECU 
does not receive any signal from the fog light switch 

P.54B-508

."

ITEM NO.

ITEM NAME

NORMAL 
CONDITION

ITEM 30

IG SW(IG1)

ON

ITEM 36

F.FOG LIGHT

ON

AC309091

MB991911

MB991827

MB991824 

AB

MB991806

MB991862

DATA LINK
CONNECTOR 
(16-PIN)

DATA LINK
CONNECTOR 
(13-PIN)

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-407

STEP 3. Check fog light relay connector A-13X for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q: Is fog light relay connector A-13X in good condition?

YES : Go to Step 4.
NO :  Repair or replace the damaged component(s). Refer 

to GROUP 00E, Harness Connector Inspection 

P.00E-2

. Verify that the fog lights illuminate normally.

STEP 4. Check the fog light relay.

Q: Is the fog light relay in good condition?

YES : Go to Step 5.
NO :  Replace the fog light relay. Verify that the fog lights 

illuminate normally.

AC204183

CONNECTOR : A-13X

RELAY BOX SIDE

AF

2 1

5

4

3

A-13X

BATTERY VOLTAGE

TESTER 
CONNECTION

SPECIFIED 
CONDITION

Not applied

4 

− 5

Open circuit

3 

− Battery (+) terminal,

1 

− Battery (-) terminal

4 

− 5

Less than 2 ohms

4

5

3

1

AC204764

1

5

4

3

2

RELAY SIDE

AB

FOG LIGHT RELAY

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-408

STEP 5. Check the battery power supply circuit to the fog 
light relay. Test at fog light relay connector A-13X.
(1) Disconnect fog light relay connector A-13X and measure at 

the voltage available at the relay box side of the connector.

(2) Measure the voltage between terminal 3 and ground, and 

also between terminal 4 and ground.

• The voltage should be approximately 12 volts (battery 

positive voltage).

Q: Is the measured voltage approximately 12 volts (battery 

positive voltage)?
YES : Go to Step 7.
NO :  Go to Step 6.

STEP 6. Check the wiring harness between fog light relay 
connector A-13X (terminals 3 and 4) and the battery.
Q: Is the wiring harness between fog light relay connector 

A-13X (terminals 3 and 4) and the battery in good 
condition?
YES : No action is necessary and testing is complete.
NO :  The wiring harness may be damaged or the 

connector(s) may have loose, corroded or damaged 
terminals, or terminals pushed back in the connector. 
Repair the wiring harness as necessary. Verify that 
the fog lights illuminate normally.

STEP 7. Check front-ECU connector A-07X for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector. 
Q: Is front-ECU connector A-07X in good condition?

YES : Go to Step 8.
NO :  Repair or replace the damaged component(s). Refer 

to GROUP 00E, Harness Connector Inspection 

P.00E-2

. Verify that the fog lights illuminate normally.

AC204183

CONNECTOR : A-13X

RELAY BOX SIDE

AF

2 1

5

4

3

A-13X

1

2

3

4

5

ACX01590AB

CONNECTOR A-13X
(RELAY BOX SIDE)

AC204183

CONNECTOR : A-13X

RELAY BOX SIDE

AF

2 1

5

4

3

A-13X

AC204183

CONNECTOR : A-07X

AB

2 1

3

4

6

7

8

9

5

11 10

RELAY BOX SIDE