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 MANUALSMITSUBISHI2004LANCER L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESINSPECTION PROCEDURE 4
2004 Mitsubishi Lancer L4-2.4L SOHC
Inspection Procedure 4
2004 Mitsubishi Lancer L4-2.4L SOHCSECTION Inspection Procedure 4
The Malfunction Indicator Lamp (SERVICE ENGINE SOON or Check Engine Lamp) Remains Illuminated and Never Goes Out.
CIRCUIT OPERATION
- The malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) power is supplied from the ignition switch.
- The ECM or PCM controls the ground of the malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) by turning the power transistor in the ECM or PCM ON and OFF.
COMMENT
- In cases such as the above, the cause is probably that the ECM or PCM is detecting a problem in a sensor or actuator, or that one of the malfunctions listed at right has probably occurred.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Short-circuit between the malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) and ECM or PCM or connector damage.
- ECM failed.
- 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. 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 continuity at combination meter harness side connector C-01.
1. Disconnect the connector C-01 and measure at the harness side.
2. Check for the continuity between terminal No. 17 and ground.
- Should be open loop.
Q: Does continuity exist?
YES: Replace the ECM or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Check harness connectors C-124 at the intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors is in good condition, repair harness wire between combination meter connector C-01 (terminal No. 17) and ECM connector C-133 or PCM connector C-134 (terminal No. 7) because of short circuit to ground. Then confirm that the malfunction symptom is eliminated.
Malfunction Indicator Lamp (SERVICE ENGINE SOON Or CHECK ENGINE LAMP) Circuit Part 1:
Malfunction Indicator Lamp (SERVICE ENGINE SOON Or CHECK ENGINE LAMP) Circuit Part 2:
CIRCUIT OPERATION
- The malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) power is supplied from the ignition switch.
- The ECM
COMMENT
- In cases such as the above, the cause is probably that the ECM
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Short-circuit between the malfunction indicator lamp (SERVICE ENGINE SOON or check engine lamp) and ECM
- ECM failed.
- 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. 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 continuity at combination meter harness side connector C-01.
1. Disconnect the connector C-01 and measure at the harness side.
2. Check for the continuity between terminal No. 17 and ground.
- Should be open loop.
Q: Does continuity exist?
YES: Replace the ECM or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Check harness connectors C-124 at the intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors is in good condition, repair harness wire between combination meter connector C-01 (terminal No. 17) and ECM connector C-133
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.