Mitsubishi Galant. Manual — part 677

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

54B-103

Inspection Procedure G-1: Seat belt warning light: Seat belt warning light does not work normally.

CIRCUIT OPERATION
The seat belt warning light illuminates when the
driver turns the ignition switch to "ON" position
without wearing the seat belt.

TECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU illuminates the seat belt warning
light according to the input signals from the following
switches:

•

Ignition switch (IG1)

•

Driver's seat belt switch

If the seat belt warning light does not illuminate, the
relevant input signal circuit, the combination meter
(seat belt warning light bulb or printed-circuit board)
or the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS

•

Malfunction of the driver's side seat belt switch

•

Malfunction of the combination meter (seat belt
warning light bulb or printed-circuit board)

•

Malfunction of the ETACS-ECU

•

Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:

•

MB991223: Test Harness Set

AC004208

Seat Belt Warning Light Circuit

AC003089 AD

CONNECTOR: C-29

AC003082AB

CONNECTORS: C-73, C-78, C-82

C-82

C-73

C-78

JUNCTION BLOCK
(FRONT VIEW)

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

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•

MB991502: Scan Tool (MUT-II)

•

MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check method of the input signal

Q: Which is to be used, the scan tool or the voltmeter to

check the input signal?
Scan tool MB991502 : Go to Step 2.
Voltmeter : Go to Step 3.

STEP 2. Check the input signal (by using scan tool
MB991502).
Check the input signals from the following switches:

•

Ignition switch (IG1)

•

Driver's side seat belt 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 relevant input signal circuit. Refer to

P.54B-9

.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the following switches:

•

Ignition switch (IG1)

•

Driver's side seat belt 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 relevant input signal circuit. Refer to

P.54B-9

.

AC003081 AB

16 PIN

MB991502

AC003083

16 PIN

AB

ETACS-ECU
TERMINAL

GROUNDED TERMINAL

MB991529

SWS DIAGNOSIS

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STEP 4. Check the seat belt warning light circuit at the
ETACS-ECU connector C-82.
(1)Disconnect the ETACS-ECU connector C-82 and measure

at the harness side.

(2)Turn the ignition switch to the "ON" position.
(3)Connect terminal 54 to the ground.

Q: Does the seat belt warning light illuminate?

YES : Replace the ETACS-ECU. The seat belt warning light

should work normally.

NO : Go to Step 5.

STEP 5. Check the seat belt warning light bulb.
Q: Is the seat belt warning light bulb in good condition?

YES : Go to Step 6.
NO : Replace it. The seat belt warning light should work

normally.

STEP 6. Check the combination meter (printed-circuit
board).
(1)Remove the combination meter.
(2)Remove the seat belt warning light bulb. Then measure the

resistance between the bulb terminals.

(3)Install the bulb to the combination meter, and then measure

the resistance between connector C-29 terminal 29 and 34.
The resistance reading at this time should be much the
same as the resistance measured at Step (2).

Q: Are the two resistance values extremely different each

other?
YES : Repair or replace the combination meter (printed

circuit board). The seat belt warning light should work
normally.

NO (much the same) : Go to Step 7.

AC002133

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

AC

CONNECTOR C-82
(HARNESS SIDE)

AC003171 AB

SEAT BELT WARNING LIGHT

AC003170

CONNECTOR C-29
(COMBINATION METER SIDE)

AB

SWS DIAGNOSIS

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SIMPLIFIED WIRING SYSTEM (SWS)

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STEP 7. Check the combination meter power supply circuit
at the combination meter connector C-29.
(1)Disconnect the combination meter connector C-29 and

measure at the harness side.

(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal 29 and ground.

Q: Is the voltage approximately 12 volts (battery positive

voltage)?
YES : Go to Step 10.
NO : Go to Step 8.

STEP 8. Check combination meter connector C-29 for
damage.
Q: Is combination meter connector C-29 in good

condition?
YES : Go to Step 9.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. The seat belt warning

light should work normally.

AC003172AB

CONNECTOR C-29
(HARNESS SIDE)

AC003089 AD

CONNECTOR: C-29