INSPECTION PROCEDURE 8: Heater control unit power supply system












COMMENTS ON TROUBLE SYMPTOM
If the heater control unit is not energised, the power supply or earth system to the ECU may be defective.

PROBABLE CAUSES

  • Malfunction of heater control unit
  • Wiring harness or connector failure

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III other system’s diagnosis code
Check that the ETACS-ECU has not set a diagnosis code.

Q. Is the diagnosis code set?
Carry out the diagnosis code procedures . Refer to GROUP 54A, ETACS-ECU .
Go to Step 2.

STEP 2. Connector check: C-60 heater control unit connector

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

STEP 3. Measure the voltage at the C-60 heater control unit connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Ignition switch: ON
(3)Voltage between terminal No. 15 and body earth
OK: System voltage

Q. Is the check result normal?
Go to Step 6.
Go to Step 4.

STEP 4. Connector check: C-317 ETACS-ECU connector

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

STEP 5. Check the wiring harness between C-60 heater control unit connector terminal No. 15 and C-317 ETACS-ECU connector terminal No. 5.

  • Check the power supply line for open circuit.

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the wiring harness.

STEP 6. Measure the voltage at the C-60 heater control unit connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Voltage between terminal No. 13 and body earth
OK: System voltage

Q. Is the check result normal?
Go to Step 8.
Go to Step 7.

STEP 7. Check the wiring harness between C-60 heater control unit connector terminal No. 13 and C-317 ETACS-ECU connector terminal No. 10.

  • Check the power supply line for open circuit.

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the wiring harness.

STEP 8. Measure the resistance at the C-60 heater control unit connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Resistance between terminal No. 14 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Replace the A/C-ECU.
Go to Step 9.

STEP 9. Check the wiring harness between C-60 heater control unit connector terminal No. 14 and body earth.

  • Check the earth wires for open circuit.

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the wiring harness.