Mitsubishi Lancer Evolution IX. Manual - part 406

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-99

STEP 8. Connector check: C-121 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Repair or replace the connector.

STEP 9. Check harness between C-137 (terminal 
No. 3) oxygen sensor (rear) 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.

AK501995

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11

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30

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10

AB

Connector: C-121

C-121 (GR)

C-121 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK305013

2 1

3

4

AB

Oxygen sensor(rear)

Connector : C-137

Harness side 
connector

C-137

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-100

STEP 10. Check harness between C-137 (terminal 
No. 4) oxygen sensor (rear) connector and C-121 
(terminal No. 26) engine-ECU connector.

• Check earthing line for damage.

Q: Is the check result normal?

YES : 

Go to Step 11 .

NO : 

Repair the damaged harness wire.

STEP 11. 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

).

AK305013

2 1

3

4

AB

Oxygen sensor(rear)

Connector : C-137

Harness side 
connector

C-137

AK501995

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3

4

5

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11

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19

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30

21

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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-101

Code No. P0170: Abnormal Fuel System

OPERATION

• Refer to P0201 injector circuit 

P.13A-105

.

• Refer to P0202 injector circuit 

P.13A-111

.

• Refer to P0203 injector circuit 

P.13A-117

.

• Refer to P0204 injector circuit 

P.13A-123

.

FUNCTION

• If the fuel system goes out of order, the fuel cor-

rection value will become larger.

• The engine-ECU checks whether the fuel correc-

tion value is within the standard limits.

TROUBLE JUDGMENT

Check Condition

• In learning air-fuel ratio

Judgment Criteria

• Fuel injection amount correction value remains 

unusually low for more than 5 seconds. 

or 

• Fuel injection amount correction value remains 

unusually high for more than 5 seconds.

PROBABLE CAUSES

• Failed fuel supply system

• Failed oxygen sensor (front)

• Failed intake air temperature sensor

• Failed air flow sensor

• Failed purge control solenoid valve

• Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-II/III diagnosis code

Q: Is any other diagnosis code than P0170 output?

YES : 

Inspection Chart for Diagnosis Code (Refer 

to 

P.13A-17

).

NO : 

Go to Step 2 .

STEP 2. M.U.T.-II/III data list

• Refer to Data List Reference Table 

P.13A-372

.

a. Item No. 12: Air flow sensor
b. Item No. 13: Intake air temperature sensor

c. Item No. 21: Engine coolant temperature sen-

sor

d. Item No. 22: Barometric pressure sensor

Q: Are the check results normal?

YES : 

Go to Step 3 .

NO : 

Perform the diagnosis code classified check 
procedure for the sensor that has shown an 
abnormal data value (Refer to Inspection 
Chart for Diagnosis Codes 

P.13A-17

).

STEP 3. Check for intake of air from intake hose 
and intake manifold.

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Repair.

STEP 4. Check for leakage of exhaust emission 
from exhaust manifold.

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Repair.

STEP 5. Check throttle body (throttle valve 
portion) for contamination.

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Clean throttle body (throttle valve portion) 
(Refer to 

P.13A-395

).

STEP 6. M.U.T.-II/III data list

• Refer to Data List Reference Table 

P.13A-372

.

a. Item No. 11: Oxygen sensor (front)

Q: Is the check result normal?

YES : 

Go to Step 7 .

NO : 

Check oxygen sensor (front) system (Refer 
to Code No. P0130 

P.13A-75

).

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-102

STEP 7. Connector Check: Injector connector

a. B-22 (No. 1 injector connector).
b. B-20 (No. 2 injector connector).

c. B-18 (No. 3 injector connector).

d. B-17 (No. 4 injector connector).

Q: Are the check results normal?

YES : 

Go to Step 8 .

NO : 

Repair or replace the connector.

STEP 8. Check injector itself.

• Check Injector itself (Refer to 

P.13A-406

).

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Replace the injector.

STEP 9. Connector check: B-12X engine control 
relay connector and C-119 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 10 .

NO : 

Repair or replace the connector.

AK305012

1

2

Connector : B-17,B-18,B-20,B-22

Harness side connector

B-22(B) B-20(B) B-18(B) B-17(B)

AB

AK305003

2

1

3

4

AB

Connector : B-12X

B-12X

Harness side 
connector

Relay box’s
triangle marks

AK501994

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66

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55

AB

Connector: C-119

C-119 (GR)

C-119 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>