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Mitsubishi Montero (2004+). Manual - part 761

SYMPTOM PROCEDURES

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-301

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

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: TAIL

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

AC309091

MB991911

MB991827

MB991824

MB991806

MB991862

DATA LINK
CONNECTOR
(16-PIN)

DATA LINK
CONNECTOR
(13-PIN)

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-302

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

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

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

Q: Are normal conditions displayed on the "TAILLIGHT

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 "TAIL LIGHT
SW" : Refer to Inspection Procedure O-6 "ETACS-ECU

does not receive any signal from the taillight switch

P.54B-527

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

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 taillights

illuminate normally.

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 taillights illuminate normally.

ITEM NO.

ITEM NAME

NORMAL
CONDITION

ITEM 01

TAILLIGHT SW

ITEM 35

H/L AUTO-CUT

OFF

ITEM 70

FRONT ECU ACK

NORMAL ACK

AC309091

MB991911

MB991827

MB991824

MB991806

MB991862

DATA LINK
CONNECTOR
(16-PIN)

DATA LINK
CONNECTOR
(13-PIN)

AC204183

CONNECTOR : A-07X

2 1

11 10

RELAY BOX SIDE

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-303

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 5 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 taillights

illuminate normally.

NO : Go to Step 5.

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

A-07X (terminal 5) 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 taillights illuminate normally.

AC204183

CONNECTOR : A-07X

2 1

11 10

RELAY BOX SIDE

AC102043

CONNECTOR: A-07X
(RELAY BOX SIDE)

AC204183

CONNECTOR : A-07X

2 1

11 10

RELAY BOX SIDE

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-304

INSPECTION PROCEDURE J-2: Headlight and Taillight: Headlights (low-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 lighting switch is set to "HEAD" posi-

tion, the "HEAD" signal is sent through the col-
umn-ECU (incorporated in the column switch) to
the front-ECU. If the front-ECU receives the
"HEAD" signal through the column-ECU, the
front-ECU turns on the headlight relay (incorpo-
rated in the front-ECU), thus causing the head-
lights to illuminate. The headlights always
illuminate at low-beam by the headlight dimmer
switch automatic resetting function.

• If the SWS communication line is defective, the

front-ECU operates the headlights by using the
other communication lines (headlight backup cir-
cuit) instead of that line.

TECHNICAL DESCRIPTION (COMMENT)
If the headlights (low-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

Headlight Relay (Low-beam) Circuit

AC204183

CONNECTOR : A-07X

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