Mitsubishi Lancer Evolution IX. Manual - part 438

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-227

STEP 4. Connector check: B-12X engine control 
relay connector

Q: Is the check result normal?

YES : 

Check intermediate connector C-105, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between B-123 (terminal No. 1) oil 
feeder control valve connector and B-12X 
(terminal No. 4) engine control relay 
connector.

• Check power line for open/short 

circuit.

NO : 

Repair or replace the connector.

STEP 5. Perform voltage measurement at C-121 
engine-ECU connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: ON

• Voltage between terminal No. 32 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 7 .

NO : 

Go to Step 6 .

AK305003

2

1

3

4

AB

Connector : B-12X

B-12X

Harness side 
connector

Relay box’s
triangle marks

AK502003

1

2

AB

Connector: B-123

B-123 (B)

Harness side 
connector

AK501995

2

3

4

5

6

7

8

9

11

12

13

14

15

16

17

18

19

20

30

21

22

23

24

25

26

27

28

29

31

32

33

34

35

1

10

AB

Connector: C-121

C-121 (GR)

C-121 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-228

STEP 6. Connector check: C-121 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Check and repair harness between B-123 

(terminal No. 2) oil feeder control valve 
connector and C-121 (terminal No. 32) 
engine-ECU connector.

• Check output line for open/short 

circuit.

NO : 

Repair or replace the connector.

STEP 7. Connector check: C-121 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 8 .

NO : 

Repair or replace the connector.

AK501995

2

3

4

5

6

7

8

9

11

12

13

14

15

16

17

18

19

20

30

21

22

23

24

25

26

27

28

29

31

32

33

34

35

1

10

AB

Connector: C-121

C-121 (GR)

C-121 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK502003

1

2

AB

Connector: B-123

B-123 (B)

Harness side 
connector

AK501995

2

3

4

5

6

7

8

9

11

12

13

14

15

16

17

18

19

20

30

21

22

23

24

25

26

27

28

29

31

32

33

34

35

1

10

AB

Connector: C-121

C-121 (GR)

C-121 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-229

STEP 8. Check harness between B-123 (terminal 
No. 2) oil feeder control valve connector and 
C-121 (terminal No. 32) engine-ECU connector.

• Check output line for damage.

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Repair the damaged harness wire.

STEP 9. Check harness between B-123 (terminal 
No. 1) oil feeder control valve connector and 
B-12X (terminal No. 4) engine control relay 
connector.

NOTE: Before checking harness, check intermediate 
connector C-105, and repair if necessary.

• Check power supply line for damage.

Q: Is the check result normal?

YES : 

Go to Step 10 .

NO : 

Repair the damaged harness wire.

STEP 10. Check the trouble symptoms.

Q: Does trouble symptom persist?

YES : 

Replace the engine-ECU.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

).

AK502003

1

2

AB

Connector: B-123

B-123 (B)

Harness side 
connector

AK501995

2

3

4

5

6

7

8

9

11

12

13

14

15

16

17

18

19

20

30

21

22

23

24

25

26

27

28

29

31

32

33

34

35

1

10

AB

Connector: C-121

C-121 (GR)

C-121 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK502003

1

2

AB

Connector: B-123

B-123 (B)

Harness side 
connector

AK305003

2

1

3

4

AB

Connector : B-12X

B-12X

Harness side 
connector

Relay box’s
triangle marks

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-230

Code No. P1603: Battery Back-up Line System

OPERATION

• Power is directly supplied to the engine-ECU (ter-

minal No. 60) from the battery.

FUNCTION

• The engine-ECU is check the open circuit of bat-

tery back-up line.

TROUBLE JUDGMENT

Check Condition

• Ignition switch: "ON" 

Judgment Criterion

• The battery back-up line voltage 6 V or less.

AK501823

65

43
50

42
49

41
48
60 61

64

46 47
58 59
67 68

45

56
66

52

51

44

53

62

54

63

57

55

8

20A

Battery

W

W

B-Y

R-B

60

Engine-ECU

Relay box

Battery back-up circuit

Wire colour code
B: Black  LG: Light green  G: Green  L: Blue  W: White  Y: Yellow  SB: Sky blue  BR: Brown  O: Orange  GR: Gray
R: Red  P: Pink  V: Violet

Back-up

power supply

AB

6 <A-13> (*1) or
13 <C-31> (*2)

C-119

(MU803782)

NOTE

*1: L.H. drive vehicles
*2: R.H. drive vehicles