Mitsubishi Galant (2004+). Manual - part 1357

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-1121

2. Connect the oscilloscope probe to check harness terminal 

No. 124, No. 130, No. 136 and No. 142.

Standard Wave Pattern

Wave Pattern Observation Points

1. Check that the standard wave pattern appears when the 

EGR valve is operating.

Point A: Presence or absence of induced electromotive force 

from the motor turning. (Refer to abnormal wave pattern.)

Point B: Height of coil back electromotive force

.

Observation condition

Function

Special pattern

Pattern height

High

Pattern selector

Display

Engine condition

Revving

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

AK203304

127 126 125 124 123 122 121

133 132 131 130 129 128

140 139 138 137 136 135 134

146 145 144 143 142 141

153 152 151 150 149 148 147

AB

OSCILLOSCOPE

POWER PLANT ECU
CHECK HARNESS
CONNECTOR

AKX01607 AC

(V)

30

20

10

0

EGR VALVE
(STEPPER 
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) <3.8L ENGINE>

13B-1122

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 EGR valve and the 

PCM.

Wave pattern characteristics

• Current is not supplied to the motor coil on the open cir-

cuit side. (Voltage does not drop to 0 volt.) Furthermore, 
the induced electromotive force wave pattern at the nor-
mal side is slightly different from the normal wave pat-
tern.

IGNITION COIL AND IGNITION POWER 
TRANSISTOR

Required Special Tools:

• MB991658: Test Harness

• MB991923: Power Plant ECU Check Harness

.

Measurement Method

<Measure at the right bank (number 1, 3, 5 cylinders)>

1. Disconnect the intermediate connector B-32, and connect 

the test harness special tool (MB991658) between the sep-
arated connector.

2. Connect the oscilloscope probe to each intermediate con-

nector B-32 terminal to analyze each cylinder:

• Terminal No. 2 for the number 1 cylinder.

• Terminal No. 7 for the number 3 cylinder.

• Terminal No. 3 for the number 5 cylinder.

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

1. Disconnect the ignition coil connector, and connect test har-

ness special tool (MB991658) between the separated con-
nector. (All terminals should be connected.)

2. Connect the oscilloscope probe to ignition coil connector 

terminal No. 3.

.

AKX01608 AB

AKX01609

OPEN
CIRCUIT
SIDE

NORMAL
SIDE

AB

1

2 3

6

7 8

4 5

9 10

AK203305

OSCILLOSCOPE

MB991658

B-32 INTERMEDIATE
CONNECTOR

AB

1 2 3

AK203306

IGNITION COIL
CONNECTOR

OSCILLOSCOPE

MB991658

AD

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-1123

Alternate method (Measure at the PCM)

1. Disconnect the all PCM connectors, and connect check har-

ness special tool (MB991923) between the separated con-
nectors.

2. Connect the oscilloscope probe to each check harness con-

nector terminal to analyze each cylinder:

• Terminal No. 151 for the number 1 cylinder.

• Terminal No. 150 for the number 2 cylinder.

• Terminal No. 144 for the number 3 cylinder.

• Terminal No. 148 for the number 4 cylinder.

• Terminal No. 143 for the number 5 cylinder.

• Terminal No. 134 for the number 6 cylinder.

Standard Wave Pattern

Observation condition

Function

Special pattern

Pattern height

Low

Pattern selector

Display

Engine r/min

Idle speed

AK202954

127 126 125 124 123 122 121

133 132 131 130 129 128

140 139 138 137 136 135 134

146 145 144 143 142 141

153 152 151 150 149 148 147

AB

POWER PLANT ECU 
CHECK HARNESS CONNECTOR

MB991923

PCM

AK203307

127 126 125 124 123 122 121

133 132 131 130 129 128

140 139 138 137 136 135 134

146 145 144 143 142 141

153 152 151 150 149 148 147

AB

OSCILLOSCOPE

POWER PLANT ECU
CHECK HARNESS
CONNECTOR

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-1124

Wave Pattern Observation Points
Point: The power transistor control signal (ignition timing) is 

advanced when the engine speed is increased.

.

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

• Cause of problem

Open-circuit in ignition primary circuit

• Wave pattern characteristics

Voltage value is too low.

CONDITION OF WAVE 
PATTERN BUILD-UP 
SECTION AND MAXIMUM 
VOLTAGE

PROBABLE CAUSE

Voltage value is too low

Open-circuit in ignition primary 
circuit

AK203308

TDC

5˚BTDC

ON

TIME

AC

OFF

CRANKSHAFT
POSITION 
SENSOR OUTPUT
WAVE PATTERN

IGNITION POWER 
TRANSISTOR 
CONTROL SIGNAL 
WAVE PATTERN

Standard wave  attern

IGNITION
TIMING

DWELL 
SECTION

5

10

0

0

2 ENGINE REVOLUTIONS (1 CAMSHAFT REVOLUTION)

(VOLT)

AK203246

NORMAL WAVE
PATTERN

AC