Mitsubishi Montero (2004+). Manual - part 762

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-305

• The front-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. Use scan tool MB991958 to select "ECU COMM 
CHK" on the SWS monitor display.
Check the following ECUs:

• Column-ECU

• Front-ECU

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) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Operate scan tool MB991958 according to the procedure 

below to display "ECU COMM CHK."

1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "ECU COMM CHK."

(4) Scan tool MB991958 should show "OK" on the "ECU 

COMM CHK" menus for both the "COLUMN ECU" and the 
"FRONT ECU" menus.

Q: Is "OK" displayed on both the "COLUMN ECU" and 

"FRONT ECU" menus?
"OK" are displayed for all the items : Go to Step 2.
"NG" is displayed on the "COLUMN ECU" menu : Refer 

to Inspection Procedure A-2 "Communication with 
column switch (column-ECU) is not possible 

P.54B-35

."

"NG" is displayed on the "FRONT ECU" menu : Refer to 

Inspection procedure A-4 "Communication with 
front-ECU is not possible 

P.54B-48

."

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-306

STEP 2. Check the input signal by using "FUNCTION 
DIAG." menu of the SWS monitor.
Check the input signals from the following switches:

• Ignition switch: ON

• Lighting switch: HEAD

Operate scan tool MB991958 according to the procedure below 
to display "HEADLIGHT LO."

1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "FUNCTION DIAG."
5. Select "LIGHTING."
6. Select "HEADLIGHT LO."

Check that normal conditions are displayed on the items 
described in the table below.

Q: Are normal conditions displayed on the "HEADLIGHT 

SW", "H/L AUTO-CUT" and "FRONT ECU ACK"?
Normal conditions are displayed for all the items : Go to 

Step 3.

Normal condition is not displayed on the "HEADLIGHT 
SW" : Refer to Inspection Procedure O-6 "ETACS-ECU 

does not receive any signal from the headlight switch 

P.54B-527

."

Normal condition is not displayed on the "H/L 
AUTO-CUT" : Refer to Inspection Procedure J-9 "Headlight 

automatic shutdown function does not work normally 

P.54B-363

."

Normal condition is not displayed on the "FRONT ECU 
ACK" : Replace the front-ECU. Verify that the headlights 

(low-beam) illuminate normally.

ITEM NO.

ITEM NAME

NORMAL 
CONDITION

ITEM 00

HEADLIGHT SW

ON

ITEM 35

H/L AUTO-CUT

OFF

ITEM 70

FRONT ECU ACK

NORMAL ACK

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-307

STEP 3. Check the front-ECU connector A-07X for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q: Is the front-ECU connector A-07X 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 headlights (low-beam) 

illuminate normally.

STEP 4. Check the battery power supply circuit to the 
front-ECU. Test at front-ECU connector A-07X.
(1) Disconnect front-ECU connector A-07X and measure the 

voltage available at the relay box side of the connector.

(2) Measure the voltage 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 : Replace the front-ECU. Verify that the headlights 

(low-beam) illuminate normally.

NO :  Go to Step 5.

AC204183

CONNECTOR : A-07X

AB

2 1

3

4

6

7

8

9

5

11 10

RELAY BOX SIDE

AC204183

CONNECTOR : A-07X

AB

2 1

3

4

6

7

8

9

5

11 10

RELAY BOX SIDE

AC203320

1

2

3

4

5

6

7

8

9

10

11

CONNECTOR A-07X
(RELAY BOX SIDE)

AC

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-308

STEP 5. Check the wiring harness between front-ECU 
connector A-07X (terminal 4) and the battery.
Q: Is the wiring harness between front-ECU connector 

A-07X (terminal 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 headlights (low-beam) illuminate normally. 

INSPECTION PROCEDURE J-3: Headlight and Taillight: Headlights (high-beam) do not illuminate.

NOTE: This troubleshooting procedure requires the 
use of scan tool MB991958 and SWS monitor kit 
MB991862. For details on how to use the SWS mon-
itor, refer to "How to use SWS monitor 

P.54B-10

."

.

CIRCUIT OPERATION
When the dimmer switch is turned on, the column 
switch sends any signal to the front-ECU. Then the 
front-ECU switches the headlights from low-beam to 
high beam or vice versa.

.

TECHNICAL DESCRIPTION (COMMENT)
If the headlights (high-beam) do not illuminate nor-
mally, the column switch or the front-ECU may be 
defective.

.

TROUBLESHOOTING HINTS

• The column switch (turn-signal light and lighting 

switch) may be defective

AC204183

CONNECTOR : A-07X

AB

2 1

3

4

6

7

8

9

5

11 10

RELAY BOX SIDE

Headlight Relay (High-beam) Circuit