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 MANUALSMITSUBISHI2009LANCER L4-2.4L (4B12)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESINSPECTION PROCEDURE 15
2009 Mitsubishi Lancer L4-2.4L (4B12)
Inspection Procedure 15
2009 Mitsubishi Lancer L4-2.4L (4B12)SECTION Inspection Procedure 15
Inspection procedure 15: Acceleration shock
COMMENT
- There may be an ignition leak accompanying the increase in the spark plug demand voltage during acceleration.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the ignition system.
- Malfunction of the ECM.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
NOTE: To protect the CVT, the TCM outputs, into the ECM, the request signal to reduce the engine torque according to the operation condition. Based on the signal, the ECM closes the throttle valve, retards the ignition or carries out fuel cut. At that time, the engine output seems to temporarily reduce, but there is no malfunction. [CVT]
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 any DTC set?
YES : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 2. [CVT]
NO : Go to Step 3. [M/T]
STEP 2. Using scan tool MB991958, read the diagnostic trouble code (DTC).
NOTE: When the CVT has a malfunction, the TCM might output the request signal of reducing the engine torque in order to protect the CVT.
1. Turn the ignition switch to the "ON" position.
2. Read the TCM-DTC.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the TCM-DTC set?
YES : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 3.
STEP 3. Check the spark plugs.
Refer to On-vehicle Service - Spark Plug Check. Testing and Inspection
Q: Are there any abnormalities?
YES : Replace the spark plug. Then confirm that the malfunction symptom is eliminated.
NO : Go to Step 4.
STEP 4. Check the ignition coil.
Refer to On-vehicle Service - Ignition Coil Check. Ignition Coil Check
Q: Are there any abnormalities?
YES : Replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
NO : Check for occurrence of ignition leak. Then confirm that the malfunction symptom is eliminated.
COMMENT
- There may be an ignition leak accompanying the increase in the spark plug demand voltage during acceleration.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the ignition system.
- Malfunction of the ECM.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
NOTE: To protect the CVT, the TCM outputs, into the ECM, the request signal to reduce the engine torque according to the operation condition. Based on the signal, the ECM closes the throttle valve, retards the ignition or carries out fuel cut. At that time, the engine output seems to temporarily reduce, but there is no malfunction. [CVT]
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 any DTC set?
YES : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 2. [CVT]
NO : Go to Step 3. [M/T]
STEP 2. Using scan tool MB991958, read the diagnostic trouble code (DTC).
NOTE: When the CVT has a malfunction, the TCM might output the request signal of reducing the engine torque in order to protect the CVT.
1. Turn the ignition switch to the "ON" position.
2. Read the TCM-DTC.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the TCM-DTC set?
YES : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 3.
STEP 3. Check the spark plugs.
Refer to On-vehicle Service - Spark Plug Check. Testing and Inspection
Q: Are there any abnormalities?
YES : Replace the spark plug. Then confirm that the malfunction symptom is eliminated.
NO : Go to Step 4.
STEP 4. Check the ignition coil.
Refer to On-vehicle Service - Ignition Coil Check. Ignition Coil Check
Q: Are there any abnormalities?
YES : Replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
NO : Check for occurrence of ignition leak. 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.