Mitsubishi Galant 9G. Manual — part 942

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-68

.

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

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

.

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

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)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-69

DTC SET CONDITIONS
Logic Flow Chart

.

Check Conditions

• 3 seconds or more have passed since the ignition

switch was turned to "ON" position.

Judgement Criteria

• Mass airflow sensor output voltage has continued

to be higher than 4.9 volts for 2 seconds.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 6

− Other Monitor

P.13B-6

.

.

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.

• PCM failed.

END

MALFUNCTION

YES

YES

YES

NO

NO

NO

CONTINUOUS

FAILURE FOR 2secs

OUTPUT VOLTAGE

< 0.2V

OUTPUT VOLTAGE

> 4.9V

MONITORING

CONDITIONS

GOOD

START

AK302377

YES

NO

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-70

DIAGNOSIS

Required Special Tool:

• 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

− How to

Cope with Intermittent Malfunctions

P.00-14

.

NO : Go to Step 2.

STEP 2. Check harness connector B-10 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.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AK303015

2

1

3

4

AB

B-10 (GR)

CONNECTOR: B-10

HARNESS
CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-71

STEP 3. Check the continuity at mass airflow sensor
harness side connector B-10.

(1) Disconnect the connector B-10 and measure at the harness

side.

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

ground.

• Should be less than 2 ohms.

Q: Does continuity exist?

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

STEP 4. Check harness connector B-21 at PCM 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.

AK303015

2

1

3

4

AB

B-10 (GR)

CONNECTOR: B-10

HARNESS
CONNECTOR:
COMPONENT SIDE

2

1

3

4

AK303019

B-10 HARNESS
CONNECTOR:
COMPONENT SIDE

AB

AK303018

55

56

54 53 52 51

57

62 61 60 59 58

63

69 68 67 66 65 64

70

75 74 73 72 71

76

82 81 80 79 78 77

83

CONNECTOR: B-21

PCM

AB

HARNESS CONNECTOR:
COMPONENT SIDE

AIR CLEANER

B-21 (B)