Mitsubishi Galant 9G. Manual — part 940

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-60

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

• MB991923: Power Plant ECU Check Harness

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 11.

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-61

STEP 3. Measure the power supply voltage at mass airflow
sensor harness side connector B-10.

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

side.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 2 and ground.

• Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts)

present?
YES : Go to Step 5.
NO : Go to Step 4.

STEP 4. Check harness connector B-17X at MFI relay for
damage.

Q: Is the harness connector in good condition?

YES : Repair harness wire between MFI relay connector

B-17X (terminal No. 4) and mass airflow sensor
connector B-10 (terminal No. 2) because of open
circuit or short circuit to ground. Then go to Step 11.

NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then go to Step 11.

AK303015

2

1

3

4

AB

B-10 (GR)

CONNECTOR: B-10

HARNESS
CONNECTOR:
COMPONENT SIDE

AK303021

2

1

3

4

B-10 HARNESS
CONNECTOR:
COMPONENT SIDE

AB

1

2

3

4

AK303017

CONNECTOR: B-17X

FRONT OF VEHICLE

B-17X

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

RELAY BOX

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-62

STEP 5. Check harness connector B-22 at PCM for
damage.

Q: Is the harness connector in good condition?

YES : Go to Step 6.
NO : Repair or replace it. Refer to GROUP 00E, Harness

Connector Inspection

P.00E-2

. Then go to Step 11.

AK303016

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

CONNECTOR: B-22

B-22 (B)

PCM

AB

HARNESS CONNECTOR:
COMPONENT SIDE

AIR CLEANER

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

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STEP 6. Measure the sensor output voltage at PCM
connector B-22 by using power plant ECU check harness
special tool MB991923.

(1) Disconnect the all PCM connectors and connect power

plant ECU check harness special tool MB991923 between
the separated connectors.

(2) Turn the ignition switch to the "ON" position.

AK303016

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

CONNECTOR: B-22

B-22 (B)

PCM

AB

HARNESS CONNECTOR:
COMPONENT SIDE

AIR CLEANER

AK202956

104

96

94

95

93 92 91

99 98 97

103 102 101 100

108 107 106 105

113 112 111 110 109

AB

POWER PLANT ECU
CHECK HARNESS CONNECTOR

MB991923

PCM