Mitsubishi Lancer Evolution X. Manual - part 269

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-141

.

CIRCUIT OPERATION

• The mass airflow sensor power is supplied from 

the MFI relay (terminal No. 2), and the ground is 
provided on the ECM (terminal No. 88).

• A voltage that is according to the mass airflow 

rate is sent to the ECM (terminal No. 87) from the 
mass airflow sensor output terminal (terminal No. 
3).

.

TECHNICAL DESCRIPTION

• While the engine is running, the mass airflow 

sensor outputs voltage which corresponds to the 
mass airflow rate.

• The ECM checks whether the voltage output by 

the mass airflow sensor while the engine is run-
ning is within a specified range.

.

DESCRIPTIONS OF MONITOR METHODS

Mass airflow sensor output voltage is out of specified 

range.

.

MONITOR EXECUTION

Continuous

.

MONITOR EXECUTION CONDITIONS 
(Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored 

in memory for the item monitored below)

• Not applicable

Sensor (The sensor below is determined to be 

normal)

• Not applicable

.

AK704234

Connector: A-07

Mass airflow sensor

A-07 (GR)

AB

AK704226

Connector: A-34X

MFI relay

A-34X

AB

AK704235 AB

Connector: B-10

ECM

B-10 (GR)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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DTC SET CONDITIONS

Logic Flow Chart

Check Condition

• 3 seconds or more have passed since the ignition 

switch was turned to "ON" position.

Judgement Criterion

• Mass airflow sensor output voltage has continued 

to be higher than 4.9 volts (corresponding to an 
air flow rate of 387 g/sec) for 2 seconds.

.

FAIL-SAFE AND BACKUP FUNCTION

• None

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function − OBD-II Drive Cycle − 

Pattern 23 

P.13A-9

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

• Mass airflow sensor failed.
• Open mass airflow sensor circuit, or connector 

damage.

• ECM failed. 

End

Malfunction

No

No

No

Output voltage

< 0.2V

Output voltage

> 4.9V

Good

AK604310

No

Start

Yes

Yes

Yes

Yes

Continuous
failure for 2secs

Monitoring
conditions

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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DIAGNOSIS

Required Special Tools:

• MB991958: Scan tool (M.U.T.-III Sub Assembly)

• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A

STEP 1. Using scan tool MB991958, check data list item 10: 
Mass Airflow Sensor.

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Start the engine and run at idle.
(3) Set scan tool MB991958 to the data reading mode for item 

10, Mass Airflow Sensor.

(4) Warm up the engine to normal operating temperature: 80° C 

to 95° C (176° F to 203° F).

• The standard value during idling should be between 

1,300 and 1,650 millivolts.

• When the engine is revved, the mass airflow rate should 

increase according to the increase in engine speed.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points − How to 

Cope with Intermittent Malfunctions 

P.00-15

.

NO :  Go to Step 2.

STEP 2. Check harness connector A-07 at mass airflow 
sensor for damage.
Q: Is the harness connector in good condition?

YES : Go to Step 3.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 8.

STEP 3. Check the continuity at mass airflow sensor 
harness side connector A-07.
(1) Disconnect the connector A-07 and measure at the harness 

side.

(2) Check for the continuity between terminal No. 4 and 

ground.

• Continuity (2 ohms or less)

Q: Does continuity exist?

YES : Go to Step 7.
NO :  Go to Step 4.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

AK704236

2 1

3

4

A-07 harness 
connector: 
component side

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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STEP 4. Check harness connector B-10 at ECM for 
damage.
Q: Is the harness connector in good condition?

YES : Go to Step 5.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 8.

STEP 5. Check for open circuit between mass airflow 
sensor connector A-07 (terminal No. 4) and ECM connector 
B-10 (terminal No. 88).
Q: Is the harness wire in good condition?

YES : Go to Step 6.
NO :  Repair it. Then go to Step 8.

STEP 6. Using scan tool MB991958, check data list item 10: 
Mass Airflow Sensor.
(1) Start the engine and run at idle.
(2) Set scan tool MB991958 to the data reading mode for item 

10, Mass Airflow Sensor.

(3) Warm up the engine to normal operating temperature: 80° C 

to 95° C (176° F to 203° F).

• The standard value during idling should be between 

1,300 and 1,650 millivolts.

• When the engine is revved, the mass airflow rate should 

increase according to the increase in engine speed.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points − How to 

Cope with Intermittent Malfunctions 

P.00-15

.

NO :  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 8.

STEP 7. Check harness connector B-10 at ECM for 
damage.
Q: Is the harness connector in good condition?

YES : Replace the mass airflow sensor. Then go to Step 8.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 8.