Inspection Procedure 31: A/C-ECU power supply system <LHD>

CIRCUIT OPERATION
If a power supply is not provided to the A/C-ECU, the A/C-ECU power supply system or the earth system may be defective.

PROBABLE CAUSES

  • Malfunction of the A/C-ECU
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-106 A/C-ECU connector

Q. Is the check result normal?

Go to Step 2.

Repair the connector.

STEP 2. Voltage measurement at C-106 A/C-ECU connector.

(1)Disconnect the connector, and measure at the wiring harness side.
(2)Turn the ignition switch to the ON position.

(3)Measure the voltage between terminal 6 and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 4.

Go to Step 3.

STEP 3. Check the wiring harness between C-106 A/C-ECU connector terminal No.6 and the ignition switch (IG2).


note Prior to the wiring harness inspection, check joint connector C-31 and junction block connector C-205 and C-202, and repair if necessary.

  • Check the A/C-ECU power supply line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.

STEP 4. Voltage measurement at C-106 A/C-ECU connector.

(1)Disconnect the connector, and measure at the wiring harness side.
(2)Turn the ignition switch to the ON position.

(3)Measure the voltage between terminal 5 and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 6.

Go to Step 5.

STEP 5. Check the wiring harness between C-106 A/C-ECU connector terminal No.5 and the ignition switch (ACC).

note Prior to the wiring harness inspection, check joint connector C-32 and intermediate connector C-125, and repair if necessary.

  • Check the A/C-ECU power supply line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.

STEP 6. Voltage measurement at C-106 A/C-ECU connector.

(1)Disconnect the connector, and measure at the wiring harness side.

(2)Measure the voltage between terminal 4 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-106 A/C-ECU connector terminal No.4 and the fusible link (30).

note Prior to the wiring harness inspection, check joint connector C-32 and intermediate connector C-125, and repair if necessary.

  • Check the rear fan switch power supply line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.

STEP 8. Resistance measurement at the C-106 front power transistor connector.

(1)Disconnect the connector, and measure at the wiring harness side.

(2)Continuity between terminal 7 and body earth
OK: 2Ω 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-106 A/C-ECU connector terminal No.7 and body earth.


  • Check the A/C-ECU earth line for open circuit.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

Repair the wiring harness.