Mitsubishi 380. Manual — part 67

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-265

• MB991910: MUT-III Main Harness A

• MB991813: SWS Monitor Kit

• MB991806: SWS Monitor Cartridge

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

• MB991822: Test Probe Harness

STEP 1. Use Diagnostic Tool MB991958 to select "ECU
COMM Check" on the SWS monitor display.
Check the following ECUs:

• Column switch (column-ECU)

• Front-ECU

CAUTION

To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958. Connect special tool MB991910 before con-
necting special tool MB991812. Be sure to connect special
tool MB991806 after turning on special tool MB991824.
(1) Connect the special tool. Refer to "How to connect SWS

monitor

P.54B-13

."

(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Operate Diagnostic Tool MB991958 according to the

procedure below to display "ECU COMM Check."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "ECU COMM Check."

(4) Diagnostic Tool MB991958 should show "OK" on the "ECU

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

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

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

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

P.54B-68

."

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

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

P.54B-80

."

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC302210

COLUMN SWITCH
CONNECTOR

COLUMN SWITCH
CONNECTOR AT
HARNESS SIDE

MB991812

AB

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-266

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

(1) Operate Diagnostic Tool MB991958 according to the

procedure below to display "HEADLAMP LO."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Function Diag."
f.

Select "LIGHTING."

g. Select "HEADLAMP LO."

(2) Check that normal conditions are displayed for the items

described in the table below.

Q: Does the Diagnostic Tool MB991958 display the items

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

Step 3.

Normal condition is not displayed for "HEADLAMP SW"
:

Refer to Inspection Procedure M-5 "ETACS-ECU
does not receive any signal from the headlamp switch

P.54B-420

."

Normal condition is not displayed for "H/L AUTO-CUT" :

Refer to Inspection Procedure H-9 "Headlamp
automatic shutoff function does not work normally

P.54B-305

."

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

(low-beam) illuminate normally.

ITEM NO.

ITEM NAME

NORMAL
CONDITION

ITEM 00

HEADLAMP SW

ON

ITEM 35

H/L AUTO-CUT

OFF

ITEM 70

FRONT ECU ACK

NORMAL ACK

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC302210

COLUMN SWITCH
CONNECTOR

COLUMN SWITCH
CONNECTOR AT
HARNESS SIDE

MB991812

AB

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-267

STEP 3. Check front-ECU connector A-11X for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is front-ECU connector A-11X 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 headlamps (low-beam)

illuminate normally.

STEP 4. Check the battery power supply circuit to the
front-ECU. Measure the voltage at front-ECU connector
A-11X.
(1) Disconnect front-ECU connector A-11X and measure the

voltage available at the relay box side of the connector.

(2) Measure the voltage between terminal numbers 8 and

ground, and also between terminal 9 and ground.

• The voltage should measure 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 headlamps

(low-beam) illuminate normally.

NO : Go to Step 5.

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE

AC209364CT

5

11

9

10

8 7 6

2

4 3

1

CONNECTOR A-11X
(RELAY BOX SIDE)

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-268

STEP 5. Check the wiring harness between front-ECU
connector A-11X (terminals 8 and 9) and the battery.
Q: Is the wiring harness between front-ECU connector

A-11X (terminals 8 and 9) 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 headlamps (low-beam) illuminate normally.

INSPECTION PROCEDURE H-3: Headlamp and Taillamp: The headlamps (high-beam) do not
Illuminate normally.

NOTE: This troubleshooting procedure requires the
use of Diagnostic Tool MB991958 and SWS monitor
kit MB991813. For details on how to use the SWS
monitor, refer to "How to connect SWS monitor

P.54B-13

."

.

CIRCUIT OPERATION

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

.

TECHNICAL DESCRIPTION (COMMENT)

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

.

TROUBLESHOOTING HINTS

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

• Trouble in input signal system

• The wiring harness or connectors may have

loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector

• The front-ECU may be defective

DIAGNOSIS

Required Special Tools:

• MB991223: Harness Set

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

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

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

• MB991813: SWS Monitor Kit

• MB991806: SWS Monitor Cartridge

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

• MB991822: Test Probe Harness

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE