Mitsubishi Galant. Manual - part 321

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-509

Example 2

•

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

•

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

INJECTOR

Required Special Tools:
MB991348: Test Harness
MD998464: Test Harness
Measurement Method
<Measure at the right bank (number 1, 3, 5 cylinders)>

1. Disconnect the injector intermediate connector, and connect 

the test harness special tool (MD998464) in between.

2. Connect the oscilloscope probe to each injector 

intermediate connector terminal to analyze each cylinder:

•

Terminal 2 (black clip of special tool) for the number 1 
cylinder

•

Terminal 3 (blue clip) for the number 3 cylinder

•

Terminal 4 (white clip) for the number 5 cylinder

<Measure at the right bank (number 2, 4, 6 cylinders)>

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.)

5. Connect the oscilloscope probe to to PCM terminal 10. 

(When checking the number 5 cylinder.)

6. Connect the oscilloscope probe to PCM terminal 25. (When 

checking the number 6 cylinder.)

AKX01602

AK000063

1 2

3 4

OSCILLOSCOPE

INJECTOR INTERMEDIATE
CONNECTOR

OSCILLO

SCOPE

PROBE

AB

AK000587

OSCILLOSCOPE

OSCILLO

SCOPE

PROBE

1

2

AB

INJECTOR
CONNECTOR

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-510

Standard Wave Pattern

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

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.

Observation conditions

Function

Special pattern

Pattern height

Variable

Variable knob

Adjust while viewing the 
wave pattern

Pattern selector

Display

Engine r/min

Idle speed

CONTRAST WITH STAN-
DARD WAVE PATTERN

PROBABLE CAUSE

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

Short in the injector solenoid

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

AKX01605

WHEN IDLING

WHEN RACING

AB

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-511

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Required Special Tool:
MB991709: Test Harness
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)

1. Connect the oscilloscope probe to PCM terminals 14, 15, 

28 and 29.

Standard Wave Pattern

Wave Pattern Observation Points

1. Check that the standard wave pattern appears when the 

idle air control motor is operating. 
Point A:

Observation conditions

Function

Special pattern

Pattern height

High

Pattern selector

Display

Engine condition

Turn the ignition switch from 
"OFF"  to "ON" (without 
starting the engine).

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

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

MULTIPORT FUEL INJECTION(MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L>

13B-512

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.

Example 2

•

Cause of problem
Open circuit in the line between the idle air control motor 
and the PCM.

•

Wave pattern characteristics
Current is not supplied to the motor coil on the open circuit 
side. (Voltage does not drop to 0 volt.) Furthermore, the 
induced electromotive force wave pattern at the normal side 
is slightly different from the normal wave pattern.

IGNITION COIL AND IGNITION POWER 
TRANSISTOR

Required Special Tool:
MB991348: Test Harness Set

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

AKX01608 AB

AKX01609

OPEN
CIRCUIT
SIDE

NORMAL
SIDE

AB