Mitsubishi Eclipse. Manual - part 355

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-913

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.

AK103538

CYCLE TIME CHANGES
WITH ENGINE SPEED
CHANGES

2 ENGINE REVOLUTIONS
(1 CAMSHAFT REVOLUTION)

75˚BTDC

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-914

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 No. 2.

Alternate method (Test harness not available)
<M/T>

1. Connect the oscilloscope probe to ECM terminal No. 1. 

(When checking the number 1 cylinder.)

2. Connect the oscilloscope probe to ECM terminal No. 14. 

(When checking the number 2 cylinder.)

3. Connect the oscilloscope probe to ECM terminal No. 2. 

(When checking the number 3 cylinder.)

4. Connect the oscilloscope probe to ECM terminal No. 15. 

(When checking the number 4 cylinder.)

<A/T>

1. Connect the oscilloscope probe to PCM terminal No. 1. 

(When checking the number 1 cylinder.)

2. Connect the oscilloscope probe to PCM terminal No. 9. 

(When checking the number 2 cylinder.)

3. Connect the oscilloscope probe to PCM terminal No. 24. 

(When checking the number 3 cylinder.)

4. Connect the oscilloscope probe to PCM terminal No. 2. 

(When checking the number 4 cylinder.)

Standard Wave Pattern

Observation conditions

Function

Special pattern

Pattern height

Variable

Variable knob

Adjust while viewing the 
wave pattern

Pattern selector

Display

Engine r/min

Idle speed

AK102980

1 2

INJECTOR
CONNECTOR

MB991348

AB

OSCILLOSCOPE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-915

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.

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Required Special Tool:

• MB991709: Test Harness Set

.

CONTRAST WITH 
STANDARD 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

AC

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-916

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 No. 1, terminal No. 3, terminal No. 4 and 
terminal No. 6, respectively.

.

Alternate method (Test harness not available)
<M/T>

Connect the oscilloscope probe to ECM terminals No. 4, 
No. 5, No. 17 and No. 18.

<A/T>

Connect the oscilloscope probe to PCM terminals No. 14, 
No. 15, No. 28 and No. 29.

Standard Wave Pattern

Wave Pattern Observation Points
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 "LOCK" 
(OFF) to "ON" position (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).

AK102983AB

1 2 3
4 5 6

IDLE AIR CONTROL
MOTOR CONNECTOR

OSCILLOSCOPE

MB991709

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