Mitsubishi Galant (2004+). Manual - part 280

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-311

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 taillights 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 7 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 taillights 

illuminate normally.

NO :  Go to Step 5.

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE 

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE 

5

11

9

10

8 7 6

2

4 3

1

AC209867AB

CONNECTOR A-11X
(RELAY BOX SIDE)

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

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STEP 5. Check the wiring harness between front-ECU 
connector A-11X (terminal 7) and the battery.

Q: Is the wiring harness between front-ECU connector 

A-11X (terminal 7) 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.

AC305977AH

CONNECTOR: A-11X

RELAY BOX SIDE 

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

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INSPECTION PROCEDURE H-2: Headlight and Taillight: The headlights (low-beam) do not illuminate 
normally.

NOTE: This troubleshooting procedure requires the 
use of scan tool MB991958 and SWS monitor kit 
MB991813. For details on how to use the SWS mon-
itor, refer to "How to use SWS monitor 

P.54B-15

."

.

INPUT SIGNAL

BATTERY

FRONT-ECU

PULSE WIDTH
MODULATOR

RELAY 
BOX

HEADLIGHT
(LH)

HEADLIGHT
(RH)

· HEADLIGHT
  AUTOMATIC
  SHUTDOWN
· HEADLIGHT
  SWITCH

FIELD EFFECT
TRANSISTOR FOR
HEADLIGHT: LOW

Headlight Relay (Low-Beam) Circuit

AC305977AE

CONNECTOR: A-11X

SYMPTOM PROCEDURES

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SIMPLIFIED WIRING SYSTEM (SWS)

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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

• 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: Scan 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: Probe Harness