Mitsubishi 380. Manual - part 68

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-269

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-270

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

• Dimmer switch: ON

(1) Operate Diagnostic Tool MB991958 according to the 

procedure below to display "HEADLAMP HI."
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 HI."

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

Replace the front-ECU. Verify that the headlamps 
(high-beam) illuminate normally.

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 "DIMMER SW" : 

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

(high-beam) illuminate normally.

ITEM NO.

ITEM NAME

NORMAL CONDITION

ITEM 00

HEADLAMP SW

ON

ITEM 02

DIMMER SW

OFF (should turn "ON" 
momentarily when the 
dimmer switch is operated)

ITEM 35

H/L AUTO-CUT

OFF

ITEM 70

FRONT ECU ACK

HI-BEAM 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-271

INSPECTION PROCEDURE H-4: Headlamp and Taillamp: When the passing switch is turned "ON," the 
headlamps (low-beam or high-beam) do not illuminate.

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

."

.

TECHNICAL DESCRIPTION (COMMENT)

If both of the headlamps (low-beam and high-beam) 
do not illuminate, the input circuit from the passing 
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

STEP 1. Check the headlamps.

Q: Do the headlamps (low-beam and high-beam) illuminate 

normally?
The headlamps illuminate normally. : Go to Step 2.
Headlamps (low-beam) do not illuminate normally : 

Refer to Inspection Procedure H-2 "The headlamps 
(low-beam) do not illuminate normally 

P.54B-264

.

Headlamps (high-beam) do not illuminate normally : 

Refer to Inspection Procedure H-3 "The headlamps 
(high-beam) do not illuminate normally 

P.54B-268

.

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-272

STEP 2. Check the input signal by using "DATA LIST" 
menu of the SWS monitor.
Turn the passing switch to the "ON" position before checking 
input signals from the passing switch.

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) Operate Diagnostic Tool MB991958 according to the 

procedure below to display "COLUMN ECU."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Data List."
f.

Select "COLUMN ECU."

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

described in the table below.

Q: Does the Diagnostic Tool MB991958 display "PASSING 

SW" as normal condition?
YES : Replace the front-ECU. When the passing switch is 

turned "ON", the headlamps (low-beam and 
high-beam) should illuminate normally.

NO :  Refer to Inspection Procedure M-5 "ETACS-ECU 

does not receive any signal from the passing switch 

P.54B-420

."

ITEM NO.

ITEM NAME

NORMAL CONDITION

ITEM 03

PASSING SW

ON

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC302210

COLUMN SWITCH 
CONNECTOR

COLUMN SWITCH 
CONNECTOR AT 
HARNESS SIDE 

MB991812

AB