Mitsubishi 380. Manual - part 65

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-257

HEADLAMP AND TAILLAMP

GENERAL DESCRIPTION CONCERNING THE HEADLAMPS AND TAILLAMPS

M1549021300264

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

The following ECUs affect the functions and control 
of the headlamps and the taillamps.

FUNCTION

CONTROL ECU

Taillamps

Front-ECU, column switch

Headlamps

ETACS-ECU, front-ECU, column switch

High-beam indicator lamp

ETACS-ECU, column switch

Headlamp automatic-shutoff function

ETACS-ECU, front-ECU, column switch

Dimmer automatic reset function

Front-ECU, column switch

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-258

Taillamps and headlamps illumination

.

Taillamps
If the column switch sends a taillamp switch "ON" signal to the 
front-ECU, the front-ECU turns on its taillamp relay, causing the 
taillamps to illuminate.

NOTE: This description covers the taillamps only. In actual driv-
ing, the taillamps may be turned off due to the headlamp auto-
matic shut-off function. For the details of the headlamp 
automatic shut-off function, refer to .

.

Headlamps

If the column switch sends a headlamp switch "ON" 
signal to the front-ECU, the front-ECU turns on its 
headlamp relay (LOW), causing the low-beam 
headlamps to illuminate. If the dimmer switch is 
turned on while the headlamp relay (LOW) is on, the 
front-ECU turns on the headlamp relay (HIGH), 
causing the high-beam headlamps to illuminate.

NOTE: This description covers the headlamps only. 
In actual driving, the headlamps may be turned off 
due to the headlamp automatic shut-off function. For 
the details of the headlamp automatic shut-off func-
tion, refer to .

High-beam indicator lamp

At the same time that the high-beams are illuminated, the 
ETACS-ECU sends a signal to illuminate the high beam indica-
tor via the CAN bus line. The combination meter receives the 
transmitted signal and turns the high-beam indicator on and off.

AC306461

Headlight switch

ON

OFF

Headlight (Low)

ON

OFF

ON

OFF

Headlight 
relay (High)

ON

OFF

High-beam 
indicator light

ON

OFF

Front ECU
acknowledge

Hi-beam

ACK

OTHERS

Passing/Dimmer
switch

ON

PASS

OFF

AB

<2-bulb type>

<4-bulb type>

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-259

Headlamp automatic-shutdown function

Even if the lighting switch (taillamps switch or headlamp switch) 
is ON, the headlamps (including the taillamps) will automati-
cally go off in the following conditions to prevent the battery 
from discharging as a result of forgetting to turn off lamps.
If the ignition key is turned from "ON" to "LOCK" (OFF) or 
"ACC" position with the lighting switch turned ON, and this 
state continues for three minutes, the headlamps will automati-
cally be turned off. If the driver's seat door is opened during 
these three minutes, the headlamps will go off one second 
later.

NOTE: The headlamp automatic-shutoff function can be cus-
tomized on vehicles equipped with a multi center display (mid-
dle grade type). Refer to 

P.54B-486

.

Dimmer automatic reset function

If the headlamp switch is turned off while the high-beam 
headlamps are on, the dimmer switch will be reset. Because of 
this, the headlamps will illuminate at low beam the next time 
that they are turned on. The dimmer switch will be also reset if 
the dimmer switch is turned on unintentionally while the pass-
ing switch is operated.

AC106399

ON

OFF

ON

OFF

Dimmer
switch

Headlamp

switch

HIGH

LOW

OFF

Headlamp

AC

SYMPTOM PROCEDURES

SIMPLIFIED WIRING SYSTEM (SWS)

54B-260

INSPECTION PROCEDURE H-1: Headlamp and Taillamp: The taillamps 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 connect the 
SWS monitor, refer to "How to connect SWS monitor 

P.54B-13

."

.

CIRCUIT OPERATION

When the lighting switch is set to "TAIL" position, the 
"TAIL" signal is sent through the column-ECU (incor-
porated in the column switch) to the front-ECU. If the 
front-ECU receives the "TAIL" signal through the col-
umn-ECU, the front-ECU turns on the taillamp relay 
(incorporated in the front-ECU), thus causing the 
taillamps to illuminate.

.

TECHNICAL DESCRIPTION (COMMENT)

If the taillamps do not illuminate normally, 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

AC305977AP

CONNECTOR: A-11X