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HOMESERVICE MANUALSMITSUBISHI2005LANCER L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESINSPECTION PROCEDURE 34
2005 Mitsubishi Lancer L4-2.4L SOHC
Inspection Procedure 34
2005 Mitsubishi Lancer L4-2.4L SOHCSECTION Inspection Procedure 34
A/C system
COMMENT
- When the A/C is "ON", the battery positive voltage is applied on the ECM or PCM (terminal No.69) from the A/C-ECU.
When battery positive voltage is applied to the ECM or PCM , the ECM or PCM turns "ON" the power transistor in the ECM or PCM . The ECM or PCM delays A/C engagement momentarily while it increases idle r/min. Then the A/C compressor clutch relay coil will be energized. With this, the A/C compressor clutch relay turns "ON" and the A/C compressor clutch operates.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the A/C control system.
- Malfunction of the A/C switch.
- Improper connector contact, open circuit or short-circuited harness wire.
- ECM failed.
- PCM failed.
DIAGNOSIS
STEP 1. Check harness connector C-133, C-137 at ECM or C-134, C-138 at PCM for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 2. Check the circuit at ECM connector C-133 or PCM connector C-134 .
1. Disconnect the connector C-133 or C-134 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.16 and ground.
- Voltage should be battery positive voltage.
4. Using a jumper wire, connect terminal No.16 to ground.
- A/C compressor relay should turn "ON".
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are the measured voltage and A/C compressor relay condition normal?
YES: Go to Step 3.
NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the voltage at ECM connector C-137 or PCM connector C-138 .
1. Disconnect the connector C-137 or C-138 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.69 and ground.
- Voltage should be 1 volt or less when the A/C switch is "OFF".
- Voltage should be battery positive voltage when the A/C switch is "ON".
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?
YES: Replace the ECM or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis.
A/C Circuit:
COMMENT
- When the A/C is "ON", the battery positive voltage is applied on the ECM
When battery positive voltage is applied to the ECM
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the A/C control system.
- Malfunction of the A/C switch.
- Improper connector contact, open circuit or short-circuited harness wire.
- ECM failed.
- PCM failed.
DIAGNOSIS
STEP 1. Check harness connector C-133, C-137 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 2. Check the circuit at ECM connector C-133
1. Disconnect the connector C-133
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.16 and ground.
- Voltage should be battery positive voltage.
4. Using a jumper wire, connect terminal No.16 to ground.
- A/C compressor relay should turn "ON".
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are the measured voltage and A/C compressor relay condition normal?
YES: Go to Step 3.
NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the voltage at ECM connector C-137
1. Disconnect the connector C-137
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.69 and ground.
- Voltage should be 1 volt or less when the A/C switch is "OFF".
- Voltage should be battery positive voltage when the A/C switch is "ON".
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?
YES: Replace the ECM or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Refer to Heating and air conditioning - Introduction To Heater, Air Conditioning And Ventilation Diagnosis.
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.