Mitsubishi Galant. Manual — part 683

SWS DIAGNOSIS

TSB Revision

SIMPLIFIED WIRING SYSTEM (SWS)

54B-127

Inspection Procedure I-3: Headlight, taillight: Headlights (high-beam) do not illuminate.

AC004373

Headlight Relay (high) Drive Circuit

AC003128 AI

A-09X

CONNECTORS: A-07X, A-09X

FRONT - ECU

A-07X

HEADLIGHT
RELAY(HI)

BATTERY

AC003129 AD

CONNECTORS: A-27, A-32

A-27

A-32

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-128

CIRCUIT OPERATION
If the column switch sends the dimmer switch ON
signal to the front-ECU, the front-ECU switches the
headlights from low-beam to high-beam or vice
versa.

TECHNICAL DESCRIPTION (COMMENT)
The headlight relay (high), column switch or the
front-ECU may be defective.

NOTE: If only one of the headlights does not
illuminate, the light bulb may be burned out or the
harness wires between the light and the headlight
relay (high) may be defective. In this case, check the
circuit by referring to GROUP 90, Headlight

P.90-60

.

TROUBLESHOOTING HINTS

•

Malfunction of the headlight relay (high)

•

Malfunction of the column switch (turn-signal light
and lighting switch)

•

Malfunction of the front-ECU

•

Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:

•

MB991223: Test Harness Set

•

MB991502: Scan Tool (MUT-II)

•

MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check the headlight (low-beam) operation.

Q: Do the headlights (low-beam) illuminate normally?

YES : Go to Step 2 <when using scan tool MB991502> or 3

<when using a voltmeter>.

NO : Solve the problem first. Refer to Inspection Procedure

I-2 (

P.54B-122

).

AC003089 AC

CONNECTOR: C-05

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-129

STEP 2. Check the input signal (by using scan tool
MB991502).
Check the input signal from the dimmer switch.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before
connecting or disconnecting scan tool MB991502.
(1)Connect scan tool MB991502 to the data link connector.
(2)Check that the tone alarm of scan tool MB991502 sounds

when the input signal enters.

Q: Does the tone alarm of scan tool MB991502 sound when

the input signal enters?
YES : Go to Step 4.
NO : Check the headlight switch input circuit. Refer to

Inspection Procedure N-14 (

P.54B-258

).

STEP 3. Check the input signal (by using a voltmeter).
Check the input signal from the dimmer switch.
(1)Use special tool MB991529 to connect a voltmeter between

ground terminal 4 or 5 and ETACS-ECU terminal 9 of the
data link connector.

(2)Check that the voltmeter indicator deflects once when the

input signal enters.

Q: Does the voltmeter indicator deflect?

YES : Go to Step 4.
NO : Check the headlight switch input circuit. Refer to

Inspection Procedure N-14 (

P.54B-258

).

STEP 4. Check the headlight relay (high).

Q: Is the headlight relay (high) in good condition?

YES : Go to Step 5.
NO : Replace it. The headlights (high-beam) should

illuminate normally.

AC003081 AB

16 PIN

MB991502

AC003083

16 PIN

AB

ETACS-ECU
TERMINAL

GROUNDED TERMINAL

MB991529

BATTERY
VOLTAGE

TESTER
CONNECTION

SPECIFIED
CONDITION

Not applied

1

−

3

Continuity

1

−

Battery (+)

terminal,
3

−

Battery (

−

)

terminal

4

−

5

Continuity

1

2 3

4

5

1

3

4

5

ACX01544

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-130

STEP 5. Check the headlight relay (high) power supply
circuit at the headlight relay (high) connector A-07X.
(1)Disconnect the headlight relay (high) connector A-07X and

measure at the relay box side.

(2)Measure the voltages between terminal 3, 4 and ground.

Q: Are the voltages approximately 12 volts (battery

positive voltage)?
YES : Go to Step 8.
NO : Go to Step 6.

STEP 6. Check headlight relay (high) connector A-07X for
damage.
Q: Is headlight relay (high) connector A-07X in good

condition?
YES : Go to Step 7.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. The headlight (high-

beam) should illuminate normally.

STEP 7. Check the harness wire between headlight relay
(high) connector A-07X and battery.
Q: Is the harness wire between headlight relay (high)

connector A-07X and battery in good condition?
YES : There is no action to be taken.
NO : Repair it. The headlights (high-beam) should

illuminate normally.

1

2

3

4

5

ACX01590AE

CONNECTOR A-07X
(RELAY BOX SIDE)

AC003128 AJ

CONNECTOR: A-07X

HEADLIGHT
RELAY(HI)

BATTERY

AC003128 AJ

CONNECTOR: A-07X

HEADLIGHT
RELAY(HI)

BATTERY