Mitsubishi Galant (2004+). Manual - part 944

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-593

DTC SET CONDITIONS

Logic Flow Chart

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Check Conditions

• Engine speed is lower than 3,000 r/min.

• Accelerator pedal is open.

• Mass airflow is between 14 and 45 g/sec.

• More than 3 seconds have elapsed after the 

above-mentioned three conditions have been 
met.

• Intake air temperature is higher than −10°C 

(14

°F).

• Barometric pressure is higher than 76 kPa (22.4 

in.Hg).

• Under the closed loop air/fuel ratio control.

• Vehicle speed is 1.5 km/h (1.0 mph) or more.

• The PCM monitors for this condition for 5 cycles 

of 10 seconds each during the drive cycle.

• Short-term fuel trim is higher than −25 percent 

and lower than +25 percent.

• The cumulative mass airflow is higher than 1,638 

g.

Judgment Criteria

• The cylinder 1, 4 heated oxygen sensor (rear) 

signal frequency divided by cylinder 1, 4 heated 
oxygen sensor (front) signal frequency = 0.7 or 
more. <Federal>

or

• The cylinder 1, 4 heated oxygen sensor (rear) 

signal frequency divided by cylinder 1, 4 heated 
oxygen sensor (front) signal frequency = 0.6 or 
more. <California>

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OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 3 

− Catalytic Converter Monitor 

P.13A-5

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

• Cylinder 1, 4 side catalytic converter deteriorated.

• Cylinder 1, 4 heated oxygen sensor failed.

• Exhaust leak.

• PCM failed.

START

MONITORING

CONDITIONS

MALFUNCTION

GOOD

END

NO

NO

YES

YES

Rf > R0

CALCULATE AVERAGE FREQUENCY

RATIO (Rf = Fr/Ff) OF SPECIFIED TIMES

R0: AVERAGE THRESHOLD VALUE.

AK302038

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-594

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

STEP 1. Check for exhaust leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 7.
NO :  Go to Step 2.

STEP 2. Using scan tool MB991958, check data list item 69: 
Cylinder 1, 4 Heated Oxygen Sensor (rear).

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 

69, Cylinder 1, 4 Heated Oxygen Sensor (rear).

• Warming up the engine. When the engine is revved, the 

output voltage should repeat 0 volt and 0.6 to 1.0 volt 
alternately.

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

YES : Go to Step 3.
NO :  Refer to DTC P0136 

− Cylinder 1, 4 Heated Oxygen 

Sensor Circuit (Sensor 2) 

P.13A-247

, DTC P0137 

− 

Cylinder 1, 4 Heated Oxygen Sensor Circuit Low 
Voltage (Sensor 2) 

P.13A-265

, DTC P0138 

− Cylinder 

1, 4 Heated Oxygen Sensor Circuit High Voltage 
(Sensor 2) 

P.13A-272

, DTC P0139 

− Cylinder 1, 4 

Heated Oxygen Sensor Circuit Slow Response 
(Sensor 2) 

P.13A-278

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AK303804AB

MB991910

DATA LINK
CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-595

STEP 3. Using scan tool MB991958, check data list item 39: 
Cylinder 1, 4 Heated Oxygen Sensor (front).

(1) Start the engine and run at idle.
(2) Set scan tool MB991958 to the data reading mode for item 

39, Cylinder 1, 4 Heated Oxygen Sensor (front).

• Warming up the engine. When the engine is revved, the 

output voltage should be 0.6 to 1.0 volt.

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

YES : Go to Step 4.
NO :  Refer to DTC P0130 

− Cylinder 1, 4 Heated Oxygen 

Sensor Circuit (Sensor 1) 

P.13A-189

, DTC P0131 

− 

Cylinder 1, 4 Heated Oxygen Sensor Circuit Low 
Voltage (Sensor 1) 

P.13A-207

, DTC P0132 

− Cylinder 

1, 4 Heated Oxygen Sensor Circuit High Voltage 
(Sensor 1) 

P.13A-214

, DTC P0133 

− Cylinder 1, 4 

Heated Oxygen Sensor Circuit Slow Response 
(Sensor 1) 

P.13A-219

, DTC P0134 

− Cylinder 1, 4 

Heated Oxygen Sensor Circuit No Activity Detected 
(Sensor 1) 

P.13A-225

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STEP 4. Using scan tool MB991958, check data list item 39: 
Cylinder 1, 4 Heated Oxygen Sensor (front).

(1) Start the engine and run at idle.
(2) Set scan tool MB991958 to the data reading mode for item 

39, Cylinder 1, 4 Heated Oxygen Sensor (front).

(3) Keep the engine speed at 2,000 r/min.

• 0 − 0.4 and 0.6 − 1.0 volt should alternate 15 times or 

more within 10 seconds.

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

YES : Go to Step 5.
NO :  Replace the cylinder 1, 4 heated oxygen sensor 

(front). Then go to Step 7.

AK303804AB

MB991910

DATA LINK
CONNECTOR

MB991824

MB991827

AK303804AB

MB991910

DATA LINK
CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>

13A-596

STEP 5. 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 3 − 

Catalytic Converter Monitor 

P.13A-5

.

(2) Read the diagnostic trouble code.
Q: Is DTC P0421 set?

YES : Replace the cylinder 1, 4 side catalytic converter. 

Then go to Step 6.

NO :  The inspection is complete.

STEP 6. 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 3 − 

Catalytic Converter Monitor 

P.13A-5

.

(2) Read the diagnostic trouble code.
Q: Is DTC P0421 set?

YES : Replace the PCM. Then go to Step 7.
NO :  The inspection is complete.

STEP 7. 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 3 − 

Catalytic Converter Monitor 

P.13A-5

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0421 set?

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