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Mitsubishi Galant 9G. Manual - part 1031

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-424

STEP 14. Check the fuel pressure.
Refer to On-vehicle Service

− Fuel Pressure Test

P.13B-1179

Q: Is the fuel pressure normal?

YES : Go to Step 15.
NO : Repair it. Then go to Step 17.

STEP 15. Check for entry of foreign matter (water,
kerosene, etc.) into fuel.
Q: Are there any abnormalities?

YES : Go to Step 16.
NO : Replace the fuel. Then go to Step 17.

STEP 16. Replace the right bank injector.
(1) Replace the right bank injector.
(2) Carry out a test drive with the drive cycle pattern. Refer to

Diagnostic Function

− OBD-II Drive Cycle − Procedure 2 −

Fuel Trim Monitor

P.13B-6

(3) Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?

YES : Replace the PCM. Then go to Step 17.
NO : The inspection is complete.

STEP 17. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to

Diagnostic Function

− OBD-II Drive Cycle − Procedure 2 −

Fuel Trim Monitor

P.13B-6

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?

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

AK303055

CONNECTOR: B-01, B-03, B-04

B-01 (GR)

B-03 (GR)

B-04 (GR)

HARNESS CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-425

DTC P0172: System too Rich (bank 1)

CAUTION

If DTC P0172 has been set, TCL related DTC
U1120 is also set. After P0172 has been diag-
nosed, don't forget to erase DTC U1120.

Fuel Trim Circuit

• Refer to DTC P0201− Injector Circuit − Cylinder

P.13B-481

, P0203

− Injector Circuit − Cylinder

P.13B-504

, P0205

− Injector Circuit − Cylinder

P.13B-527

CIRCUIT OPERATION

• Refer to DTC P0201− Injector Circuit − Cylinder

P.13B-481

, P0203

− Injector Circuit − Cylinder

P.13B-504

, P0205

− Injector Circuit − Cylinder

P.13B-527

TECHNICAL DESCRIPTION

• If a malfunction occurs in the fuel system, the fuel

trim value becomes too small.

• The PCM checks whether the fuel trim value is

within a specified range.

DESCRIPTIONS OF MONITOR METHODS

Right bank air/fuel learning value (long time fuel trim)

and air/fuel feedback integral value (short time
fuel trim) are too rich.

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)

• Misfire 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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-426

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

• Under the closed loop air/fuel ratio control.

• Engine coolant temperature is higher than 76°C

(169

°F).

• Mass airflow sensor output is 8 g/sec or more.

Judgment Criteria

• Long-term fuel trim has continued to be lower

than

−12.5 percent for 5 seconds.

• Short-term fuel trim has continued to be lower

than

−7.4 percent for 5 seconds.

Check Conditions

• Under the closed loop air/fuel ratio control.

• Engine coolant temperature is higher than 76°C

(169

°F).

• Mass airflow sensor output is 8 g/sec or less.

LRN

: LONG-TERM TRIM

: SHORT-TERM TRIM

K0 : MAXIMUM LIMIT OF LONG-TERM TRIM
K1 : MAXIMUM LIMIT OF SHORT-TERM TRIM
K2 : MINIMUM LIMIT OF LONG-TERM TRIM
K3 : MINIMUM LIMIT OF SHORT-TERM TRIM

START

MONITORING

CONDITIONS

END

YES

LRN

> K0

MALFUNCTION

GOOD

LRN

< K2

< K3

> K1

CONTINUOUS FAILURE

FOR 5secs

AK204050

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-427

Judgment Criteria

• Long-term fuel trim has continued to be lower

than

−12.5 percent for 5 seconds.

• Short-term fuel trim has continued to be lower

than

−12.5 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 76°C

(169

°F).

• Under the closed loop air/fuel ratio control.

Judgment Criteria

• Long-term fuel trim has continued to be −12.5

percent for 2 seconds.

• Short-term fuel trim has continued to be −30.0

percent for 2 seconds.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 2

− Fuel Trim Monitor

P.13B-6

TROUBLESHOOTING HINTS (The most likely

causes for this code to be set are:)

• Mass airflow sensor failed.

• Injector (Number 1, 3, 5) failed.

• Incorrect fuel pressure.

• Engine coolant temperature sensor failed.

• Intake air temperature sensor failed.

• Barometric pressure sensor failed.

• Manifold absolute pressure sensor failed.

• Harness damage in right bank injector circuit, or

connector damage.

• PCM failed.

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).

• When idling, between 2.0 and 6.0 g/sec.

• When 2,500 r/min, between 8.0 and 16.0 g/sec.

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

YES : YES: Go to Step 2.
NO : Refer to DTC P0101

− Mass Airflow Circuit

Range/Performance Problem

P.13B-46