Inspection Procedure 23: A/C Load signal system








OPERATION



  • The A/C load signal is inputted to the engine-A/T-ECU (terminal No. 78) from the A/C-ECU (terminal No. 12).

FUNCTION



  • The magnitude of the A/C compressor load is detected and input to the engine-A/T-ECU. The engine-A/T-ECU provides A/C idle up control according to the A/C compressor load condition.

PROBABLE CAUSES



  • Failed A/C-ECU
  • Open/short circuit in A/C load signal circuit or loose connector contact
  • Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at D-216 engine-A/T-ECU connector.

  • Measure engine-A/T-ECU terminal voltage.
  • Engine: Idling
  • A/C switch: ON (A/C compressor in driven state)
  • Voltage between terminal No. 78 and earth.
OK:
    1 V or less (when the temperate around the atmospheric air temperature sensor is 18°C or more, and the A/C is set to the lowest temperature and the maximum air flow rate)
    System voltage (when the A/C is set to the temperature in the cabin and the minimum air flow rate)

Q. Is the check result normal?
Go to Step 2 .
Go to Step 4 .

STEP 2. Connector check: D-216 engine-A/T-ECU connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-A/T-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 4. Connector check: D-216 engine-A/T-ECU connector


Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Perform voltage measurement at D-08 A/C-ECU connector.

  • Measure A/C-ECU terminal voltage.
  • Engine: Idling

  • A/C set temperature:

      • Maximum Cool when temperature in cabin is 25°C or more
      Maximum Hot when temperature in cabin is 25°C or less
  • Voltage between terminal No. 12 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 8 .
Go to Step 6 .

STEP 6. Connector Check: D-08 A/C-ECU connector

Q. Is the check result normal?
Go to Step 7 .
Repair or replace the connector.

STEP 7. Check harness between D-08 (terminal No. 12) A/C-ECU connector and D-216 (terminal No. 78) engine-A/T-ECU connector.
note Before checking harness, check intermediate connector D-230, and repair if necessary.

  • Check output line for short circuit.

Q. Is the check result normal?
Check A/C system (Refer to GROUP 55 - Troubleshooting - Check Chart for Trouble Symptoms ).
Repair the damaged harness wire.

STEP 8. Connector check: D-08 A/C-ECU connector

Q. Is the check result normal?

    Check intermediate connector D-230, and repair if necessary. If intermediate connector is normal, check and repair harness between D-08 (terminal No. 12) A/C-ECU connector and D-216 (terminal No. 78) engine-A/T-ECU connector.

    • Check output line for open circuit.
Repair or replace the connector.