Mitsubishi Grandis. Manual - part 720

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-131

OPERATION

• Power is supplied to the injector (terminal No. 1) 

from the engine control relay (terminal No. 1).

• The engine-ECU <M/T> or engine-A/T-ECU 

<A/T> (terminal No. 21) makes the power 
transistor in the unit be in ON position, and that 
makes currents go on the injector (terminal No. 
2).

FUNCTION

• The engine-ECU <M/T> or engine-A/T-ECU 

<A/T> connector controls the power supply 
interval of the injector.

• The fuel injection amount of the injector depends 

on the power supply interval.

TROUBLE JUDGMENT

Check Condition

• While engine is running.

Judgment Criterion

• Injector coil surge voltage (battery positive 

voltage + 2 V) has not been detected for 2 
seconds.

PROBABLE CAUSE

• Failed No. 4 injector

• Open/short circuit in No. 4 injector circuit or loose 

connector contact

• Failed engine-ECU <M/T>

• Failed engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. MUT-III actuator test

• Item 04: No. 4 injector

OK: Idling state varies.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

).

NO : 

Go to Step 2 .

STEP 2. Connector check: B-105 No. 4 injector 
connector

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Repair or replace.

STEP 3. Check No. 4 injector itself.

• Check No. 4 Injector (Refer to 

P.13A-393

) itself.

Q: Is the check result normal? 

YES : 

Go to Step 4 .

NO : 

Replace No. 4 injector.

STEP 4. Perform voltage measurement at B-105 
No. 4 injector connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: ON 

• Voltage between terminal No. 1 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Go to Step 5 .

AK300978

M

1

2

AM

B-105 (GR)

Harness side connector

Connector: B-105

AK300978

M

1

2

AM

B-105 (GR)

Harness side connector

Connector: B-105

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-132

STEP 5. Connector check: B-15X engine control 
relay connector

Q: Is the check result normal? 

YES : 

Check intermediate connector C-116, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between B-15X (terminal No. 1) 
engine control relay connector and B-105 
(terminal No. 1) No. 4 injector connector.

• Check power supply line for 

open/short circuit and damage.

NO : 

Repair or replace.

STEP 6. Connector check: B-15X engine control 
relay connector

Q: Is the check result normal? 

YES : 

Go to Step 7.

NO : 

Repair or replace.

STEP 7. Check harness between B-15X (terminal 
No. 1) engine control relay connector and B-105 
(terminal No. 1) No. 4 injector connector.

NOTE: Before checking harness, check intermediate 
connector C-116, and repair if necessary. 

• Check power supply line for damage.

Q: Is the check result normal?

YES : 

Go to Step 8 .

NO : 

Repair.

AK300967

2

1

3

4

AC

Harness side
connector

B-15X

Connector: B-15X

Relay box’s
triangle marks

AK300978

M

1

2

AM

B-105 (GR)

Harness side connector

Connector: B-105

AK300967

2

1

3

4

AC

Harness side
connector

B-15X

Connector: B-15X

Relay box’s
triangle marks

AK300967

2

1

3

4

AC

Harness side
connector

B-15X

Connector: B-15X

Relay box’s
triangle marks

AK300978

M

1

2

AM

B-105 (GR)

Harness side connector

Connector: B-105

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-133

STEP 8. Connector check: C-110 engine-ECU 
<M/T> connector or engine-A/T-ECU <A/T> 
connector

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Repair or replace.

STEP 9. Check harness between B-105 (terminal 
No. 2) No. 4 injector connector and C-110 
(terminal No. 21) engine-ECU <M/T> connector or 
engine-A/T-ECU <A/T> connector.

• Check output line for open/short circuit and 

damage.

Q: Is the check result normal? 

YES : 

Go to Step 10 .

NO : 

Repair.

AK305618AB

1

2

3

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5

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21

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26

27

Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector

AK300978

M

1

2

AM

B-105 (GR)

Harness side connector

Connector: B-105

AK305618AB

1

2

3

4

5

6

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21

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Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-134

STEP 10. Perform signal wave pattern 
measurement at C-110 engine-ECU <M/T> 
connector or engine-A/T-ECU <A/T> connector 
(Using an oscilloscope).

• Engine: Idling

• Transmission: Neutral <M/T> or P range <A/T>

• Voltage between terminal No. 21 and earth.

OK: Waveform should be display on 
Inspection procedure using an oscilloscope 
(Refer to 

P.13A-378

).

Q: Is the check result normal? 

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

).

NO : 

Replace engine-ECU <M/T> or 
engine-A/T-ECU <A/T>.

AK305618AB

1

2

3

4

5

6

7

8

9

10

11

12

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26

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Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector