Mitsubishi Galant. Manual — part 179

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-397

CIRCUIT OPERATION

•

The ignition coil is energized by Battery positive
voltage from the ignition switch through the
ignition failure sensor.

•

When the PCM turns off its internal power
transistor, battery positive voltage is applied to
the ignition power transistor (terminal 3) inside
the ignition coil, causing the ignition power
transistor to be turned on.

•

If the ignition power transistor is turned on, the
primary circuit of the ignition coil is energized by
grounding the ignition coil through terminal 2,
causing the primary current to flow to the ignition
coil.

TROUBLESHOOTING HINTS (The most likely
causes for this case:)

•

Malfunction of the ignition coil.

•

Malfunction of the ignition power transistor.

•

Malfunction of the ignition failure sensor.

ACX02471

CONNECTOR:B-01

IGNITION
FAILURE
SENSOR

AH

AK000631AC

CONNECTOR:C-73

AK000639AB

B-23

B-09

CONNECTORS:B-09,B-23

AK000633 AE

CONNECTOR:C-04

AK000280

CONNECTORS : C-39, C-40

C-39 C-40

PCM

AU

AK000632 AB

CONNECTOR:C-66

AK000634 AB

CONNECTOR:C-58

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-398

•

Improper connector contact, open circuit or short-
circuited harness wire.

•

Malfunction of the PCM.

DIAGNOSIS

STEP 1. Check the ignition failure sensor.
Refer to GROUP 16, Ignition System

−

On-vehicle service

−

Ignition failure sensor check(

P.16-34

).

Q: Are there any abnormalities?

YES : Go to Step 2.
NO : Replace the ignition failure sensor. Then confirm that

the malfunction symptom is eliminated.

STEP 2. Check the ignition coil.
Refer to GROUP 16, Ignition System

−

On-vehicle service

−

Ignition coil check(

P.16-33

).

Q: Are there any abnormalities?

YES : Go to Step 3.
NO : Replace the ignition coil. Then confirm that the

malfunction symptom is eliminated.

STEP 3. Check harness connectors B-01 at ignition failure
sensor for damage.
Q: Is the harness connector in good condition?

YES : Go to Step 4.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection(

P.00E-2

). Then confirm that the

malfunction symptom is eliminated.

ACX02471

CONNECTOR:B-01

IGNITION
FAILURE
SENSOR

AH

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-399

STEP 4. Using the oscilloscope, check the ignition failure
sensor.
(1) Disconnect the ignition failure sensor connector B-01, and

connect test harness special tool (MB991658) in between.
(All terminals should be connected.)

(2) Connect the oscilloscope probe to the ignition failure sensor

side connector terminal 3.

(3) Start the engine and run at idle.
(4) Check the waveform.

•

The waveform should show a pattern similar to the
illustration.

(5) Turn the ignition switch to the "LOCK"(OFF) position.

Q: Is the waveform normal?

YES : Go to Step 11.
NO : Go to Step 5.

STEP 5. Check the power supply voltage at ignition failure
sensor harness side connector B-01.
(1) Disconnect the connectors B-01 and measure at the

harness side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 4 and ground.

•

Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK"(OFF) position.

Q: Is the voltage normal?

YES : Go to Step 6.
NO : Check connectors C-04, C-66 and C-73 at

intermediate connectors for damage, and repair or
replace as required. Refer to GROUP 00E, Harness
Connector Inspection (

P.00E-2

). If intermediate

connectors are in good condition, repair harness wire
between ignition switch connector C-58 terminal 2
and ignition failure sensor connector B-01 terminal 4
because of open circuit. Then confirm that the
malfunction symptom is eliminated.

AK000411AB

OSCILLOSCOPE
PROBE

IGNITION FAILURE
SENSOR CONNECTOR

OSCILLOSCOPE

1 2 3 4

AK000412

NORMAL WAVEFORM (AT IDLING)

NOTE : CYCLE (T) SHORTENS AS
THE ENGINE SPEED RISES

(V)

15

14

13

AK000412AB

T

AK000413AC

4 3 2 1

B-01 HARNESS
SIDE CONNECTOR

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L>

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STEP 6. Check harness connector B-09, B-23 at ignition
coil for damage.
Q: Is the harness connector in good condition?

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

Connector Inspection(

P.00E-2

). Then confirm that the

malfunction symptom is eliminated.

STEP 7. Check the power supply voltage at ignition coil
connectors B-09, B-23.
(1) Disconnect the connector B-09, B-23 and measure at the

harness side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 1 and ground.

•

Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK"(OFF) position.

Q: Is the voltage normal?

YES : Go to Step 8.
NO : Repair harness wire between ignition failure

connectors B-01 terminal 3 and ignition coil
connectors B-09, B-23 terminals 1 because of open
circuit. Then confirm that the malfunction symptom is
eliminated.

STEP 8. Check the circuit at ignition coil harness side
connector B-09, B-23.
(1) Disconnect the connectors B-09, B-23 and measure at the

harness side.

(2) Engine cranking.
(3) Measure the voltage between terminal 3 and ground.

•

Voltage should be 0.3 and 3.0 volts.

(4) Turn the ignition switch to the "LOCK"(OFF) position.

Q: Is the voltage normal?

YES : Repair harness wire or harness damage between

ignition coil connector B-09, B-23 terminal 2 and
ground because of open circuit or harness damage.
Then confirm that the malfunction symptom is
eliminated.

NO : Go to Step 9.

AK000639AB

B-23

B-09

CONNECTORS:B-09,B-23

AK000414

3 2 1

B-09,B-22
HARNESS SIDE
CONNECTOR

AC

AK000415AC

1

2

3

B-09,B-22 HARNESS
SIDE CONNECTOR