Mitsubishi Galant. Manual - part 186

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-425

Wave Pattern Observation Points
Check that cycle time T becomes shorter when the engine 

speed increased.

Examples of Abnormal Wave Patterns
Example 1

•

Cause of problem
Sensor interface malfunction.

•

Wave pattern characteristics
Rectangular wave pattern is output even when the engine is 
not started.

Example 2

•

Cause of problem
Loose timing belt.
Abnormality in sensor disc.

•

Wave pattern characteristics
Wave pattern is displaced to the left or right.

AK000062

CYCLE TIME CHANGES

WITH ENGINE SPEED

CHANGES

2 ENGINE REVOLUTIONS (1 CAMSHAFT REVOLUTION)

75˚BTDC

142˚

58˚

63˚ 49˚

5˚BTDC

T

Standard wave pattern

CRANKSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

CAMSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

TIME

TDC: TOP DEAD CENTER

NO.1 TDC

NO.2 TDC

NO.3 TDC

NO.4 TDC

0

0

(V)

AB

AKX01597

AKX01602

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-426

INJECTOR

Required Special Tools:
MD991348: Test Harness Set
Measurement Method
1. Disconnect the injector connector, and connect the test 

harness special tool MB991348 in between. (All terminals 
should be connected.)

2. Connect the oscilloscope probe to injector connector 

terminal 2.

Alternate method (Test harness not available)

1. Connect the oscilloscope probe to PCM terminal 1. (When 

checking the number 1 cylinder.)

2. Connect the oscilloscope probe to PCM terminal 9. (When 

checking the number 2 cylinder.)

3. Connect the oscilloscope probe to PCM terminal 24. (When 

checking the number 3 cylinder.)

4. Connect the oscilloscope probe to PCM terminal 2. (When 

checking the number 4 cylinder.)

Standard Wave Pattern

Wave Pattern Observation Points
Point A: Height of injector coil induced voltage.

Observation conditions

Function

Special pattern

Pattern height

Variable

Variable knob

Adjust while viewing the 
wave pattern

Pattern selector

Display

Engine r/min

Idle speed

AK000587

OSCILLOSCOPE

OSCILLO

SCOPE

PROBE

1

2

AB

INJECTOR
CONNECTOR

AKX01604

(V)

50

0

DRIVE SIGNAL:"ON"

POINT B:
INJECTOR DRIVE 
TIME

POINT A

DRIVE SIGNAL:"OFF"

POWER VOLTAGE

INJECTION COIL INDUCED
VOLTAGE (APPROXIMATELY 50-60 V)

AB

Standard wave pattern

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-427

Point B: Injector drive time

1. The injector drive time should be synchronized with the 

scan tool tester display.

2. When the engine is suddenly revved, the drive time will be 

greatly extended at first, but the drive time will soon return 
to original length.

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Required Special Tool:
MB991709: Test Harness Set
Measurement Method
1. Disconnect the idle air control motor connector, and connect 

the test harness special tool, MB991709 in between. (All 
terminals should be connected.)

2. Connect the oscilloscope probe to the idle air control motor 

connector terminal 1, terminal 3, terminal 4 and terminal 6, 
respectively.

Alternate method (Test harness not available)
Connect the oscilloscope probe to PCM terminals 14, 15, 28 

and 29.

Standard Wave Pattern

CONTRAST WITH 
STANDARD WAVE 
PATTERN

PROBABLE CAUSE

Injector coil induced voltage is 
low or doesn't appear at all

Short in the injector solenoid

AKX01605

WHEN IDLING
WHEN RACING

AC

Observation conditions

Function

Special pattern

Pattern height

High

Pattern selector

Display

Engine condition

Turn the ignition switch from 
"LOCK" (OFF)  to "ON" posi-
tion (without starting the en-
gine).

While the engine is idling, 
turn the A/C switch to "ON."

Immediately after starting the 
warm the engine 
(approximately one minute).

AKX01606

6

3

1 2
4 5

OSCILLOSCOPE

OSCILLOSCOPE PLOBE

AKX01606AB

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-428

Wave Pattern Observation Points
Check that the standard wave pattern appears when the idle air 

control motor is operating. 
Point A:

Presence or absence of induced electromotive force from the 

motor turning. (Refer to abnormal wave pattern.)

Point B:

Height of coil back electromotive force

Examples of Abnormal Wave Patterns
Example 1

•

Cause of problem
Malfunction of motor. (Motor is not operating.)

•

Wave pattern characteristics
Induced electromotive force from the motor turning does not 
appear.

CONTRAST WITH 
STANDARD WAVE 
PATTERN

PROBABLE CAUSE

Induced electromotive force 
does not appear or is 
extremely small

Malfunction of motor

CONTRAST WITH STAN-
DARD WAVE PATTERN

PROBABLE CAUSE

Coil reverse electromotive 
force does not appear or is 
extremely small

Short in the coil

AKX01607 AB

(V)

30

20

10

0

IAC
MOTOR
CONTROL
SIGNAL
WAVE
PATTERN

THE WAVE PATTERN
APPEARS FOR AN
INSTANT, BUT SOON
DISAPPEARS.

POINT B COIL RE-
VERSE ELECTRO-
MOTIVE FORCE
(APPROXIMATELY
3 x10 V)

POINT AN INDUCED
ELECTROMOTIVE
FORCE FROM THE
MOTOR TURNING

TIME

Standard wave pattern

AKX01608 AB