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Mitsubishi Montero (2004+). Manual - part 257

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-515

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 3

− Catalytic Converter Monitor

P.13A-4

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

• Right bank side catalytic converter deteriorated.

• Right bank heated oxygen sensor failed.

• Exhaust leak.

• PCM failed.

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991911: Main Harness B

STEP 1. Check the exhaust leaks.
Q: Are there any abnormalities?

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

STEP 2. Using scan tool MB991958, check data list item 69:
Heated Oxygen Sensor Bank 1, Sensor 2 (right 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, Heated Oxygen Sensor Bank 1, Sensor 2 (right 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

− Heated Oxygen Sensor Circuit

(Bank 1, Sensor 2)

P.13A-222

, DTC P0137

− Heated

Oxygen Sensor Circuit Low Voltage (Bank 1, Sensor
2)

P.13A-238

, DTC P0138

− Heated Oxygen Sensor

Circuit High Voltage (Bank 1, Sensor 2)

P.13A-245

DTC P0139

− Heated Oxygen Sensor Circuit Slow

Response (Bank 1, Sensor 2)

P.13A-250

AK302970

MB991911

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-516

STEP 3. Using scan tool MB991958, check data list item 39:
Heated Oxygen Sensor Bank 1, Sensor 2 (right front).
(1) Start the engine and run at idle.
(2) Set scan tool MB991958 to the data reading mode for item

39, Heated Oxygen Sensor Bank 1, Sensor 2 (right 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

− Heated Oxygen Sensor Circuit

(Bank 1, Sensor 1)

P.13A-167

, DTC P0131

− Heated

Oxygen Sensor Circuit Low Voltage (Bank 1, Sensor
1)

P.13A-184

, DTC P0132

− Heated Oxygen Sensor

Circuit High Voltage (Bank 1, Sensor 1)

P.13A-191

DTC P0133

− Heated Oxygen Sensor Circuit Slow

Response (Bank 1, Sensor 1)

P.13A-196

, DTC P0134

− Heated Oxygen Sensor Circuit No Activity Detected

(Bank 1, Sensor 1)

P.13A-202

STEP 4. Using scan tool MB991958, check data list item 39:
Heated Oxygen Sensor Bank 1, Sensor 1 (right front).
(1) Start the engine and run at idle.
(2) Set scan tool MB991958 to the data reading mode for item

39, Heated Oxygen Sensor Bank 1, Sensor 1 (right 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 right bank heated oxygen sensor (front).

Then go to Step 7.

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-4

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

YES : Replace the right bank side catalytic converter. Then

go to Step 6.

NO : The inspection is complete.

AK302970

MB991911

MB991824

MB991827

AK302970

MB991911

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-517

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-4

(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-4

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

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

DTC P0431: Warm up catalyst Efficiency Below Threshold (bank 2)

TECHNICAL DESCRIPTION

• The signal from the rear heated oxygen sensor

differs from the front heated oxygen sensor. That
is because the catalytic converter purifies
exhaust gas. When the catalytic converter has
deteriorated, the signal from the front heated oxy-
gen sensor becomes similar to the rear heated
oxygen sensor.

• The PCM compares the output of the front and

rear heated oxygen sensor signals.

DESCRIPTIONS OF MONITOR METHODS
Front and rear heated oxygen sensor rich/lean

switching frequencies are nearly equal.

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)

• Heated oxygen sensor (front) monitor

• Heated oxygen sensor (rear) monitor

• Heated oxygen sensor heater (front) monitor

• Heated oxygen sensor heater (rear) monitor

• Misfire monitor

• EGR system monitor

• Fuel system monitor

• Air/fuel ratio feedback monitor

Sensor (The sensor below is determined to be

normal)

• Volume airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

• Barometric pressure sensor

• Throttle position sensor

• Accelerator pedal position sensor

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-518

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

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

• The accelerator is not closed.

• Volume airflow sensor output frequency is

between 69 and 169 Hz.

• 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 mph) or more.

• The PCM monitors for this condition for 7 cycles

of 12 seconds each during the drive cycle.

• Short-term fuel trim is higher than −30 percent

and lower than +25 percent.

• The cumulative volume airflow sensor output fre-

quency for every 2 seconds is higher than 4,000
Hz.

Judgment Criteria

• The left bank heated oxygen sensor (rear) signal

frequency divided by left bank heated oxygen
sensor (front) signal frequency = 0.75 or more.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function

− OBD-II Drive Cycle −

Procedure 3

− Catalytic Converter Monitor

P.13A-4

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

• Left bank side catalytic converter deteriorated.

• Left bank heated oxygen sensor failed.

• Exhaust leak.

• PCM failed.

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

START

MONITORING

CONDITIONS

Rf > R0

MALFUNCTION

GOOD

END

YES

CALCULATE AVERAGE FREQUENCY

RATIO (Rf = Fr/Ff) OF SPECIFIED TIMES

R0: AVERAGE THRESHOLD VALUE.
R1: REAL TIME THRESHOLD VALUE.

AK302952

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