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 MANUALSMITSUBISHI2004ECLIPSE L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESINSPECTION PROCEDURE 34
2004 Mitsubishi Eclipse L4-2.4L SOHC
Inspection Procedure 34
2004 Mitsubishi Eclipse 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 (terminals No. 45) PCM (terminals No. 83) from the automatic compressor controller. 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 rpm. 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 functions.
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.
- Malfunction of the ECM or PCM .
DIAGNOSIS
STEP 1. Check connector C-49, C-53 at ECM or connector C-50, C-57 at PCM for damage.
Q: Is the 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-49 or PCM connector C-50 .
1. Disconnect the connectors C-49 or C-50 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 8 or No. 20 and ground.
- Voltage should be battery positive voltage.
4. Using a jumper wire, connect terminal No. 8 or No. 20 to ground.
- A/C compressor relay should turn "ON".
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the 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 circuit at ECM connector C-53 or PCM connector C-57 .
1. Disconnect the connectors C-53 or C-57 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 45 or No. 83 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 voltage normal?
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 Part 1:
COMMENT
- When the A/C is "ON", the battery positive voltage is applied on the ECM (terminals No. 45)
With this, the A/C compressor clutch relay turns "ON", and the A/C compressor clutch functions.
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.
- Malfunction of the ECM
DIAGNOSIS
A/C Circuit Part 2:
STEP 1. Check connector C-49, C-53 at ECM
Q: Is the 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-49
1. Disconnect the connectors C-49
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 8
- Voltage should be battery positive voltage.
4. Using a jumper wire, connect terminal No. 8
- A/C compressor relay should turn "ON".
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the 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 circuit at ECM connector C-53
1. Disconnect the connectors C-53
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 45
- 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 voltage normal?
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.