Mitsubishi Lancer Evolution X. Manual - part 289

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-221

DTC SET CONDITIONS
Logic Flow Chart

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Check Conditions

• Engine coolant temperature is between − 10° C 

(14° F) and 60° C (140° F) when the engine is 

started.

• Intake air temperature is − 10° C (14° F) or higher.
• The intake air temperature subtracted from the 

intake air temperature when the engine is started 
is lower than 10° C (18° F).

• The total time when the amount of intake air is 

small is less than the specified time.

Judgement Criterion

• After the estimated engine coolant temperature 

rises above 77° C (171° F), the actual engine 

coolant temperature is less than 77° C (171° F) 

even though the specified time has passed.

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FAIL-SAFE AND BACKUP FUNCTION

• None

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OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function − OBD-II Drive Cycle − 

Pattern 9 

P.13A-9

.

.

End

Yes

Malfunction

Estimate engine coolant temp.

Good

Specified time has passed?

No

No

 

Monitoring 
conditions

Actual engine coolant
temp. >= 77˚C (171˚F)

Estimated engine coolant

temp. >= 77˚C (171˚F)

No

AK900356

Start

Yes

No

Yes

YES

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-222

TROUBLESHOOTING HINTS (The most 
likely causes for this code to be set are:)

• The engine cooling system is faulty.
• ECM failed. 

DIAGNOSIS

STEP 1. Check the cooling system.
Refer to GROUP 14, Engine Cooling Diagnosis 

P.14-3

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Q: Is the cooling system normal?

YES : Replace the ECM. When the ECM is replaced, 

register the ID code. Refer to GROUP 42B, ID Code 
Registration Necessity Judgment Table <Vehicles 
with KOS> 

P.42B-11

 or GROUP 42C, ID Codes 

Registration Judgment Table <Vehicles with WCM> 

P.42C-9

. Then go to Step 2.

NO :  Repair it. Then go to Step 2.

STEP 2. Test the OBD-II drive cycle.
(1) Carry out test drive with the drive cycle pattern. Refer to 

Diagnostic Function − OBD-II Drive Cycle − Pattern 9 

P.13A-9

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0128 set?

YES : Retry the troubleshooting.
NO :  The inspection is complete.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-223

13A

DTC P0131: Heated Oxygen Sensor (front) Circuit Low Voltage

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AK704249

1

2

3 4 5 6 7 8 9 10 11 12 13 14 15 16

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

1 2
3 4

1

10 111213 14

19 20

2 3 4

7 8 9

2

8

7

6

5

4

3

11

21

20

19

18

17

16

15

14

13

12

9

22

1

10

0.5 V

AB

1

4

2

3

39

SKY BLUE

SKY BLUE

38

HEATED OXYGEN SENSOR (FRONT) CIRCUIT

B-09

C-34

6

RED

RED

7

A-13

HEATED OXYGEN SENSOR
(FRONT)

FROM MFI RELAY

TO ECM

ENGINE
CONTROL
MODULE

AK704229AB

Connector: A-13

A-13

AK704227

Connector: B-09

ECM

B-09 (GR)

AB

AK704228

AB

Heated oxygen
sensor (front)

Connector: C-34

C-34 (B)

SRS-ECU

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the ECM (ter-
minal No. 38) from the output terminal (terminal 
No. 3) of the heated oxygen sensor (front).

• Terminal No. 4 of the heated oxygen sensor 

(front) is grounded with ECM (terminal No. 39).

• The ECM applies an offset voltage of 0.5 volt to 

terminal No. 4 of the heated oxygen sensor 
(front).

.

TECHNICAL DESCRIPTION

• The heated oxygen sensor (front) detects the 

concentration of oxygen in the exhaust gas; it 
converts those data to voltage, and inputs the 
resulting signals to the ECM.

• When the heated oxygen sensor (front) begins to 

deteriorate, the heated oxygen sensor signal 
response becomes poor.

• The ECM checks for the heated oxygen sensor 

(front) output voltage.

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DESCRIPTIONS OF MONITOR METHODS

Heated oxygen sensor (front) output voltage is under 

the specified range.

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MONITOR EXECUTION

Continuous

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MONITOR EXECUTION CONDITIONS 
(Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored 

in memory for the item monitored below)

• Heated oxygen sensor (front) heater monitor
• Misfire monitor
• Fuel system monitor
• Heated oxygen sensor (rear) feedback control 

system monitor

Sensor (The sensor below is determined to be 

normal)

• Mass airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
• Barometric pressure sensor
• Throttle position sensor
• Accelerator pedal position sensor

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