Mitsubishi Eclipse / Eclipse Spyder (2000-2002). Service and repair manual - part 335

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L ENGINE>

13B-539

Standard Wave Pattern

Wave Pattern Observation Points

1. 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.

Observation conditions

Function

Special pattern

Pattern height

Low

Pattern selector

Display

Engine r/min

Idle speed

AKX01600

2 ENGINE REVOLUTIONS (1 CAMSHAFT REVOLUTION)

75

BTDC

5

BTDC

T

CYCLE TIME CHANGES
WITH ENGINE SPEED
CHANGES

CRANKSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

CAMSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

TDC: TOP DEAD CENTER

NO.1 TDC

NO.2 TDC

NO.3 TDC

NO.4 TDC

NO.5 TDC

NO.6 TDC

TIME

Standard wave pattern

AB

AKX01597

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L ENGINE>

13B-540

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 ECM <M/T> or PCM 

<A/T> terminal 1. (When checking the number 1 cylinder.)

2. Connect the oscilloscope probe to ECM <M/T> or PCM 

<A/T> terminal 9. (When checking the number 2 cylinder.)

3. Connect the oscilloscope probe to ECM <M/T> or PCM 

<A/T> terminal 24. (When checking the number 3 cylinder.)

4. Connect the oscilloscope probe to ECM <M/T> or PCM 

<A/T> terminal 2. (When checking the number 4 cylinder.)

5. Connect the oscilloscope probe to ECM <M/T> or PCM 

<A/T> terminal 10. (When checking the number 5 cylinder.)

6. Connect the oscilloscope probe to ECM <M/T> or PCM 

<A/T> terminal 25. (When checking the number 6 cylinder.)

AKX01602

AK000063

1 2

3 4

OSCILLOSCOPE

INJECTOR INTERMEDIATE
CONNECTOR

OSCILLO

SCOPE

PROBE

AB

AK000064

OSCILLOSCOPE

OSCILLO

SCOPE

PLOBE

1 2

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L ENGINE>

13B-541

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 
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

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.0L ENGINE>

13B-542

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 ECM <M/T> or PCM <A/

T> 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:

Presence or absence of induced electromotive force from the 

motor turning. (Refer to abnormal wave pattern.)

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