Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMITSUBISHI2005LANCER L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESINSPECTION PROCEDURE 22
2005 Mitsubishi Lancer L4-2.4L SOHC
Inspection Procedure 22
2005 Mitsubishi Lancer L4-2.4L SOHCSECTION 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 Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 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 the DTC set?
YES: Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO: Go to Step 2.
STEP 2. Check the ignition timing.
Refer to On-vehicle Service - Ignition Timing Check.
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.
STEP 3. Using scan tool MB991958, check data list.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 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 Data List Reference Table. Data List Reference Table & Normal Scan Data Values
a. Item 21: Engine Coolant Temperature Sensor.
b. Item 13: Intake Air Temperature Sensor.
c. Item 25: Barometric pressure Sensor.
d. Item 59: Heated Oxygen Sensor (rear).
e. Item 11: 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 it. Then confirm that the malfunction symptom is eliminated.
STEP 4. Using scan tool MB991958, check data list.
1. Turn the ignition switch to the "ON" position.
2. Check the following items of the data list. Refer to Data List Reference Table. Data List Reference Table & Normal Scan Data Values
a. Item 11: Heated Oxygen Sensor (front).
- Voltage should fluctuate between 0 - 0.4 volt and 0.6 - 1.0 volt 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 On-vehicle Service - Fuel Pressure Test.
Q: Is the fuel pressure normal?
YES: Go to Step 6.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
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 and spark plugs.
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 eliminated?
YES: The check is completed.
NO: Replace the catalytic converter. Then confirm that the malfunction symptom is eliminated.
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 Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 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 the DTC set?
YES: Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO: Go to Step 2.
STEP 2. Check the ignition timing.
Refer to On-vehicle Service - Ignition Timing Check.
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.
STEP 3. Using scan tool MB991958, check data list.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 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 Data List Reference Table. Data List Reference Table & Normal Scan Data Values
a. Item 21: Engine Coolant Temperature Sensor.
b. Item 13: Intake Air Temperature Sensor.
c. Item 25: Barometric pressure Sensor.
d. Item 59: Heated Oxygen Sensor (rear).
e. Item 11: 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 it. Then confirm that the malfunction symptom is eliminated.
STEP 4. Using scan tool MB991958, check data list.
1. Turn the ignition switch to the "ON" position.
2. Check the following items of the data list. Refer to Data List Reference Table. Data List Reference Table & Normal Scan Data Values
a. Item 11: Heated Oxygen Sensor (front).
- Voltage should fluctuate between 0 - 0.4 volt and 0.6 - 1.0 volt 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 On-vehicle Service - Fuel Pressure Test.
Q: Is the fuel pressure normal?
YES: Go to Step 6.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
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 and spark plugs.
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 eliminated?
YES: The check is completed.
NO: Replace the catalytic converter. Then confirm that the malfunction symptom is eliminated.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.