Mitsubishi Eclipse. Manual - part 356

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-917

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 ECM or 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 STANDARD 
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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-918

Measurement Method
1. Disconnect the ignition coil connector, and connect test 

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

2. Connect the oscilloscope probe to ignition coil connector 

terminal No. 3.

.

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

Connect the oscilloscope probe to ECM terminal No. 10 (for 
number 1 

− number 4), terminal No. 23 (for number 2 − 

number 3) respectively.

<A/T>

Connect the oscilloscope probe to PCM terminals No. 11 
(for number 1 

− number 4), terminal No. 12 (for number 2 − 

number 3) respectively.

Standard Wave Pattern

Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum 

voltage (Refer to abnormal wave pattern examples 1 and 2.

Observation conditions

Function

Special pattern

Pattern height

Low

Pattern selector

Display

Engine r/min

Approximately 1,200 r/min

AK102984AB

1

2

3

IGNITION COIL
CONNECTOR

OSCILLOSCOPE

MB991348

AK000068

θ

(V)

T

REVOLUTION TIME CORRESPONDING
TO A CRANK ANGLE OF 180˚
COMPRESSION TOP DEAD CENTER

T:

75˚BTDC

5˚BTDC

6

CRANKSHAFT
POSITION 
SENSOR OUTPUT
WAVE PATTERN

4

2

0

6

T

1

θ: SPARK

ADVANCE
ANGLE

IGNITION PERIOD

IGNITION POWER 
TRANSISTOR 
CONTROL SIGNAL 
WAVE PATTERN

4

2

0

OFF

ON

DWELL 
SECTION

TIME

T

1

: TIME COMPUTED BY THE ECM or PCM

Standard wave pattern

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-919

.

Examples of Abnormal Wave Patterns
Example 1 (Wave pattern during engine cranking)

• Cause of problem

Open-circuit in ignition primary circuit

• Wave pattern characteristics

Top-right part of the build-up section cannot be seen, and 
voltage value is approximately 2 volts too low.

Example 2 (Wave pattern during engine cranking)

• Cause of problem

Malfunction in ignition power transistor

• Wave pattern characteristics

Power voltage results when the ignition power transistor is 
ON.

CONDITION OF WAVE PATTERN 
BUILD-UP SECTION AND 
MAXIMUM VOLTAGE

PROBABLE CAUSE

Rises from approximate 2 volts to 
approximate 4.5 volts at the top-right

Normal

2-volt rectangular wave

Open-circuit in 
ignition primary circuit

Rectangular wave at power voltage

Ignition power 
transistor malfunction

AKX01612

NORMAL WAVE
PATTERN

2V

AB

AKX01613

BATTERY
POSITION
VOLTAGE

NORMAL WAVE
PATTERN

AB

SPECIAL TOOLS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L>

13A-920

SPECIAL TOOLS

M1131000600524

TOOL

TOOL NUMBER AND 
NAME

SUPERSESSION

APPLICATION

MB991958
A: MB991824
B: MB991827
C: MB991910
D: MB991911
E: MB991914
F: MB991825
G: MB991826
MUT-III sub assembly
A: Vehicle 
Communication Interface 
(V.C.I.)
B: MUT-III USB Cable
C: MUT-III Main Harness 
A (Vehicles with CAN 
communication system)
D: MUT-III Main Harness 
B (Vehicles without CAN 
communication system)
E: MUT-III Main Harness 
C (for Chrysler models 
only)
F: MUT-III Adapter 
Harness
G: MUT-III Trigger 
Harness

• Reading diagnostic 

trouble code

• MFl system inspection

• Measurement of fuel 

pressure

CAUTION

For vehicles with CAN 
communication, use 
MUT-III main harness A 
to send simulated 
vehicle speed. If you 
connect MUT-III main 
harness B instead, the 
CAN communication 
does not function 
correctly.

MB991348
Test harness set

MB991348-01

• Adjustment of throttle 

position sensor

• Inspection using an 

oscilloscope

MB991910

MB991826

MB991958

MB991911

MB991914

MB991824

MB991827

MB991825

DO NOT USE

A

B

C

D

E

F

G

DO NOT USE

MB991348