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Mitsubishi Galant 9G. Manual - part 743

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-414

STEP 11. Check for harness damage between cylinder 1, 4
injector connector and PCM connector.

a. Check the harness wire between injector connector B-01

(terminal No. 2) and PCM connector B-23 (terminal No.
153) at No. 1 cylinder injector.

b. Check the harness wire between injector connector B-27

(terminal No. 2) and PCM connector B-23 (terminal No.
139) at No. 4 cylinder injector.

Q: Is the harness wire in good condition?

YES : Go to Step 12.
NO : Repair it. Then go to Step 15.

STEP 12. Check the fuel pressure.
Refer to On-vehicle Service

− Fuel Pressure Test

P.13A-1124

Q: Is the fuel pressure normal?

YES : Go to Step 13.
NO : Repair it. Then go to Step 15.

STEP 13. Check for entry of foreign matter (water,
kerosene, etc.) into fuel.
Q: Are there any abnormalities?

YES : Replace the fuel. Then go to Step 15.
NO : Go to Step 14.

AK303822

B-01 (GR)

B-27 (GR)

CONNECTORS: B-01, B-27

HARNESS CONNECTOR:
COMPONENT SIDE

127 126 125 124 123 122 121

133 132 131 130 129 128

140 139 138 137 136 135 134

146 145 144 143 142 141

153 152 151 150 149 148 147

AK303058

HARNESS CONNECTOR:
COMPONENT SIDE

CONNECTOR: B-23

B-23

PCM

AIR CLEANER

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

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STEP 14. Replace the cylinder 1, 4 injector.
(1) Replace the cylinder 1, 4 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.13A-6

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

YES : Replace the PCM. Then go to Step 15.
NO : The inspection is complete.

STEP 15. 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.13A-6

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

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

DTC P0172: System too Rich (cylinder 1, 4)

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 1

P.13A-464

, DTC P0204

− Injector Circuit-cylinder

P.13A-494

CIRCUIT OPERATION

• Refer to DTC P0201 − Injector Circuit-cylinder 1

P.13A-464

, DTC P0204

− Injector Circuit-cylinder

P.13A-494

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

Cylinder 1, 4 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

AK303822

B-01 (GR)

B-27 (GR)

CONNECTORS: B-01, B-27

HARNESS CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-416

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 6 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

−10.0 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 6 g/sec or less.

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

−15.0 percent for 5 seconds.

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) <2.4L ENGINE>

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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 −25.0

percent for 2 seconds.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 2

− Fuel Trim Monitor

P.13A-6

TROUBLESHOOTING HINTS (The most likely

causes for this code to be set are:)

• Mass airflow sensor failed.

• Injector (Number 1, 4) 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 cylinder 1, 4 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 6.5 and 14.5 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.13A-46