Inspection Procedure 34
A/C system.
COMMENT
- When the A/C is "ON" the battery positive voltage is applied on the ECM (terminal 83)
When battery positive voltage is applied to the ECM
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
STEP 1. Check connector C-111, C-122 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-111
1. Disconnect the connectors C-111
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 20 and ground.
- Voltage should be battery positive voltage.
4. Using a jumper wire, connect terminal 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 Diagnosis - 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-122
1. Disconnect the connectors C-122
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 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 Diagnosis - Introduction To Heater, Air Conditioning And Ventilation Diagnosis.