Mitsubishi 380. Manual - part 640

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-652

INSPECTION PROCEDURE USING AN 
OSCILLOSCOPE

M1131154501085

CAMSHAFT POSITION SENSOR AND 
CRANKSHAFT POSITION SENSOR

Required Special Tools:

• MB992044:  ECU Check Harness

.

Measurement Method

1. Disconnect the all ECU connectors, and connect check 

harness special tool (MB992044) between the separated 
connectors.

2. Connect the oscilloscope to check harness terminal No. 38. 

(Check the camshaft position sensor signal wave pattern.)

3. Connect the oscilloscope to check harness terminal No. 23. 

(Check the crankshaft position sensor signal wave pattern.)

Standard Wave Pattern

Observation condition

Function

Special pattern

Pattern height

Low

Pattern selector

Display

Engine r/min

Idle speed

03DB243A

B-20 HARNESS 

CONNECTOR 

OSCILLOSCOPE

03DB244A

B-20 HARNESS 

CONNECTOR 

OSCILLOSCOPE

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-653

Wave Pattern Observation Points

1. Check that cycle time 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.

03DB259A

Standard wave pattern

CRANKSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

CAMSHAFT

POSITION

SENSOR OUTPUT

WAVE PATTERN

2 ENGINE REVOLUTIONS (1 CAMSHAFT REVOLUTION)

(VOLT)

5

0

5

0

No. 1TDC

No. 3TDC

No. 4TDC

No. 2TDC

(TIME)

AKX01597

AKX01602

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-654

INJECTOR

Required Special Tools:

• MB991658: Test Harness
• MB992044: ECU Check Harness

.

Measurement Method 1

Perform a Power balance Test on all cylinders.
1. Connect MUT III to vehicle and go to Data item list.

2. Scroll to Item No. 72, Absolute load value and lock. Also 

lock Item No. 2, Crank angle sensor (engine speed).

3. Go to Actuator test and select Item No. 1, No.1 Injector. 

4. Start engine and allow to idle. 

5. Perform actuator test on each injecto from 1 to 6 and record 

the engine load and speed during each actuator test.

6. Check recorded values for variations between cylinders. If 

all injectors are operating correctly there should be minimal 
difference between load and engine speed values for all 
cylinders.

.

Measurement Method 2

<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 
separated connector.

2. Connect the oscilloscope probe to each intermediate 

connector B-32 terminal to analyze each cylinder:

• Terminal No. 5 for the number 1 cylinder

• Terminal No. 10 for the number 3 cylinder

• Terminal No. 4 for the number 5 cylinder

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

1. Disconnect the injector connector, and connect the test har-

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

2. Connect the oscilloscope probe to injector connector termi-

nal No. 2.

Alternate method (Measure at the ECU)

Disconnect the all ECU connectors, and connect check har-
ness special tool (MB992044) between the separated con-
nectors.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AK302166

1 2

INJECTOR

CONNECTOR

MB991658

OSCILLOSCOPE

AB

1 2 3
6 7 8

4 5
9 10

AK203300

OSCILLOSCOPE

MB991658

B-32 INTERMEDIATE

CONNECTOR

AB

MULTIPORT FUEL INJECTION (MPI) DIAGNOSIS

MULTIPORT FUEL INJECTION (MPI) <3.8L ENGINE>

13A-655

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

nector terminal to analyze each cylinder:

• Terminal No. 153 for the number 1 cylinder.

• Terminal No. 146 for the number 2 cylinder.

• Terminal No. 140 for the number 3 cylinder.

• Terminal No. 139 for the number 4 cylinder.

• Terminal No. 133 for the number 5 cylinder.

• Terminal No. 127 for the number 6 cylinder.

Standard Wave Pattern

Wave Pattern Observation Points
Point A: Height of injector coil induced voltage.

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

03DB145A

OSCILLOSCOPE

POWER PLANT ECU

CHECK HARNESS

CONNECTOR

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