Inspection Procedure 23: A/C load signal system








OPERATION



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

PROBABLE CAUSES



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

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at D-213 engine-ECU connector.

  • Measure engine-ECU terminal voltage.
  • Engine: Idling
  • A/C switch: ON (A/C compressor in driven state)
  • Voltage between terminal No. 12 and earth.
OK:
    The output voltage being 1V or less and being equal to the system voltage is alternately repeated.

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

STEP 2. Connector check: D-213 engine-ECU connector

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

STEP 3. Check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - Precautions Before Service - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ). After registering the injector identification code, the vehicle equipped with the closed type DPF carries out the forcible DPF regeneration. (Refer to GROUP 17 - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 4. Connector check: D-213 engine-ECU connector


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

STEP 5. Connector Check: D-08 A/C-ECU connector

Q. Is the check result normal?
Go to Step 6 .
Repair or replace.

STEP 6. Check harness between D-08 (terminal No. 12) A/C-ECU connector and D-213 (terminal No. 12) engine-ECU connector.
note Before checking harness, check intermediate connector D-230, and repair if necessary.

  • Check output line for open/short circuit and damage.

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