Mitsubishi Eclipse. Manual — part 356

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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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

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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

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MULTIPORT FUEL INJECTION (MFI) <2.4L>

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.

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

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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