Mitsubishi Montero (2002-2004). Manual — part 753

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SYMPTOM PROCEDURES

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INSPECTION PROCEDURE 21: Dieseling (Run-on).

.

COMMENT

• Fuel leakage from injectors is suspected, or car-

bon build up.

.

TROUBLESHOOTING HINTS (The most likely
causes for this case: )

• Fuel leakage from injectors.

DIAGNOSIS

STEP 1. Check the injectors for fuel leakage.
Replace the leaking injector. Then confirm that the malfunction

symptom is eliminated.

INSPECTION PROCEDURE 22: Too high CO and HC concentration when idling

.

COMMENT

• Abnormal air/fuel ratio is suspected.

.

TROUBLESHOOTING HINTS (The most likely
causes for this case: )

• Malfunction of air/fuel ratio control system.

• Deteriorated catalyst.

DIAGNOSIS

Required Special Tool:

• MB991502: Scan Tool (MUT-II)

STEP 1. Using scan tool MB991502, read the diagnostic
trouble code (DTC).

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC set?

YES : Refer to GROUP 13A, Diagnostic Trouble Code Chart

P.13Ab-22

.

NO : Go to Step 2.

STEP 2. Check the ignition timing.
Refer to GROUP 11A, On-vehicle Service

− Ignition Timing

Check

P.11A-6

.

Q: Is the ignition timing normal?

YES : Go to Step 3.
NO : Check that the crankshaft position sensor and timing

belt cover are in the correct position. Then confirm
that the malfunction symptom is eliminated.

ACX01539

16-PIN

MB991502

AC

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SYMPTOM PROCEDURES

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STEP 3. Using scan tool MB991502, check data list.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Check the following items in the data list. Refer to GROUP

13A, Data List Reference Table

P.13Ab-29

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a. Item 21: Engine Coolant Temperature Sensor.
b. Item 13: Intake Air Temperature Sensor.

c. Item 25: Barometric pressure Sensor.

d. Item 69: Right Bank Heated Oxygen Sensor (rear).
e. Item 39: Right Bank Heated Oxygen Sensor (front).

f. Item 59: Left Bank Heated Oxygen Sensor (rear).

g. Item 11: Left Bank Heated Oxygen Sensor (front).

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

YES : Go to Step 4.
NO : Repair or replace. Then confirm that the malfunction

symptom is eliminated.

STEP 4. Using scan tool MB991502, check data list.
(1) Turn the ignition switch to the "ON" position.
(2) Check the following items of the data list. Refer to GROUP

13A, Data List Reference Table

P.13Ab-29

.

a. Item 39: Right Bank Heated Oxygen Sensor (front).
b. Item 11: Left Bank Heated Oxygen Sensor (front).

• Voltage should fluctuate between 0 − 0.4 volts and 0.6 −

1.0 volts while idling after the engine has been warmed.

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

YES : Replace the heated oxygen sensor (front). Then

confirm that the malfunction symptom is eliminated. If
not resolved, go to step 6.

NO : Go to Step 5.

STEP 5. Check the fuel pressure.
Refer to GROUP 13A, On-vehicle Service

− Fuel Pressure Test

P.13Aa-13

.

Q: Is the fuel pressure normal?

YES : Go to Step 6.
NO : Repair or replace. Then confirm that the malfunction

symptom is eliminated.

ACX01539

16-PIN

MB991502

AC

ACX01539

16-PIN

MB991502

AC

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SYMPTOM PROCEDURES

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STEP 6. Check the following items.
(1) Check the following items, and repair or replace the

defective items.

a. Check the injectors for fuel leakage.
b. Check the ignition coil, spark plugs, spark plug cables.

c. Check compression pressure.

d. Check the positive crank case ventilation system.
e. Check the evaporative emission system.

f. Check the EGR system.

(2) Then check the malfunction symptom.
Q: Is the malfunction symptom is eliminated.

YES : The check is completed.
NO : Replace the catalytic converter. Then confirm that the

malfunction symptom is eliminated.

INSPECTION PROCEDURE 23: Transient, Mass Emission Tailpipe Test Failure.

.

COMMENT

• The test is failed when the air/fuel ratio is not con-

trolled to the ideal air/fuel ratio. This occurs due
to the feedback control by heated oxygen sensor
signals, insufficient EGR flow rate, or deteriorated
catalyst.

NOTE: If the three-way catalyst temperature is low
when checking the exhaust gas, the three-way cata-
lyst cannot sufficiently clean the emissions. Warm up
the engine sufficiently before checking the exhaust,
and check immediately.

.

TROUBLESHOOTING HINTS (The most likely
causes for this case: )

• Malfunction of air/fuel ratio control system.

• Malfunction of the EGR system.

• Deteriorated catalyst.

DIAGNOSIS

Required Special Tool:

• MB991502: Scan Tool (MUT-II)

STEP 1. Check the exhaust gas with the engine at normal
operating temperature.
Q: After enough warm up, was the exhaust gas checked

enough?
YES : Go to Step 2.
NO : Check it again after enough warm up.

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SYMPTOM PROCEDURES

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STEP 2. Check the following items.
(1) Check the following items.

a. Check all vacuum hoses and connectors.
b. Check electrical wires and connectors for obvious prob-

lems.

c. Check the exhaust system for missing or damaged

parts.

Q: Are they normal?

YES : Go to Step 3.
NO : Repair or replace. Then confirm that the malfunction

symptom is eliminated.

STEP 3. Check the driveability.
(1) Check if the malfunction symptom described on the

symptom chart is occurring.

Q: Is the driveability normal?

YES : Go to Step 4.
NO : Refer to GROUP 13A, Trouble Symptom Chart

P.13Ab-26

.

STEP 4. Using scan tool MB991502, read the diagnostic
trouble code (DTC).

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC set?

YES : Refer to GROUP 13A, Diagnostic Trouble Code Chart

P.13Ab-22

.

NO : Go to Step 5.

STEP 5. Check the ignition timing.
Refer to GROUP 11A, On-vehicle Service

− Ignition Timing

Check

P.11A-6

.

Q: Is the ignition timing normal?

YES : Go to Step 6.
NO : Check that the crankshaft position sensor and timing

belt cover are in the correct position. Then confirm
that the malfunction symptom is eliminated.

ACX01539

16-PIN

MB991502

AC