Mitsubishi Galant (2004+). Manual - part 1087

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-41

.

CIRCUIT OPERATION

• The mass airflow sensor power is supplied from 

the MFI relay (terminal No. 4), and the ground is 
provided on the PCM (terminal No. 69).

• 5-volt power is applied to the mass airflow sensor 

output terminal (terminal No. 3) from the PCM 
(terminal No. 108).

.

TECHNICAL DESCRIPTION

• While the engine is running, the mass airflow 

sensor outputs voltage which corresponds to the 
mass airflow rate.

• The PCM 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
Compare load value with mass airflow sensor output 

voltage.

.

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)

• Throttle position sensor

.

AK303012

CONNECTOR: B-10

MASS AIRFLOW SENSOR

AB

B-10 (GR)

AK303013

CONNECTORS: B-21, B-22

PCM

AB

AIR CLEANER

B-22 (B)

B-21 (B)

1

2

3

4

1

2

3

4

1

2

3

4

1

2

3

4

AK303014

CONNECTOR: B-17X

MFI RELAY

MFI RELAY

FRONT OF VEHICLE

B-17X

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-42

DTC SET CONDITIONS <Range/Performance problem - low input>

Logic Flow Chart

.

Check Conditions

• Throttle position sensor output voltage is 1.5 volt 

or higher.

Judgement Criteria

• Mass airflow sensor output voltage has continued 

to be 1.82 volts or lower for 2 seconds.

.

START

END

NO

YES

YES

YES

NO

NO

MALFUNCTION

GOOD

CONTINUOUS

FAILURE FOR 2secs

OUTPUT VOLTAGE

< =1.82V

MONITORING

CONDITIONS

AK302376

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-43

DTC SET CONDITIONS <Range/Performance problem - high input>

Logic Flow Chart

.

Check Conditions

• Throttle position sensor output voltage is 1.0 volt 

or lower.

Judgement Criteria

• Mass airflow sensor output voltage has continued 

to be 3.5 volts or higher for 2 seconds.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13B-5

.

.

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

• Mass airflow sensor failed.

• Mass airflow sensor circuit harness damage, or 

connector damage.

• PCM failed. 

START

END

NO

NO

YES

YES

YES

NO

MALFUNCTION

GOOD

CONTINUOUS

FAILURE FOR 2secs

OUTPUT VOLTAGE

> =3.50V

MONITORING

CONDITIONS

AK302375

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-44

DIAGNOSIS

Required Special Tools:

• MB991958: Scan tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

STEP 1. Using scan tool MB991958, check data list item 12: 
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 

12, 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 2.0 

and 6.0 g/sec.

• 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 

P.00-6

.

NO :  Go to Step 2.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827