Inspection Procedure 1

INSPECTION PROCEDURE 1: Malfunction of the A/C-ECU Power Supply System.

A/C-ECU Power Supply Circuit (Part 1):

A/C-ECU Power Supply Circuit (Part 2):

PROBABLE CAUSES
- Malfunction of connector.
- Malfunction of the harness.
- Malfunction of the A/C-ECU.

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check A/C-ECU connector C-15 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is A/C-ECU connector C-15 in good condition?

YES : Go to Step 2.

NO : Repair or replace the connector.

STEP 2. Check the wiring harness for open circuit.







1. Disconnect A/C-ECU connector C-15 and the battery harness, and measure at the wiring harness side.







2. Measure the resistance between A/C-ECU connector C-15 terminal 3 and battery.

OK: Less than 10 ohms

Q: Is the check result normal?

YES : Go to Step 4.

NO : Go to Step 3.

STEP 3. Check the wiring harness between A/C-ECU connector C-15 (terminal 3) and the battery.










NOTE: Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described.

Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 3) and the battery in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness.

STEP 4. Check A/C-ECU connector C-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is A/C-ECU connector C-20 in good condition?

YES : Go to Step 5.

NO : Repair or replace the connector.

STEP 5. Check the wiring harness for open circuit.







1. Disconnect A/C-ECU connector C-20, and measure the resistance at the wiring harness side.







2. Measure the resistance between A/C-ECU connector C-20 terminal 36 and ignition switch connector.

OK: Less than 10 ohms

Q: Is the check result normal?

YES : Go to Step 7.

NO : Go to Step 6.

STEP 6. Check the wiring harness between A/C-ECU connector C-20 (terminal 36) and the ignition switch (ACC).










NOTE: Also check intermediate connector C-24 and joint connector C-01 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 and joint connector C-01 is damaged, repair or replace the connector as described.

Q: Is the wiring harness between A/C-ECU connector C-20 (terminal 36) and the ignition switch (ACC) in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness.

STEP 7. Check the wiring harness for open circuit.







1. Disconnect A/C-ECU connector C-20, and measure the resistance at the wiring harness side.







2. Measure the resistance between A/C-ECU connector C-20 terminal 27 and ground.

OK: Less than 10 ohms

Q: Is the check result normal?

YES : Go to Step 9.

NO : Go to Step 8.

STEP 8. Check the wiring harness between A/C-ECU connector C-20 (terminal 27) and ground.







Q: Is the wiring harness between A/C-ECU connector C-20 (terminal 27) and ground in good condition?

YES : It can be assumed that this malfunction is intermittent.

NO : Repair the wiring harness.

STEP 9. Retest the system

Check that the A/C works normally.

Q: Is the check result satisfactory?

YES : It can be assumed that this malfunction is intermittent.

NO : Replace the A/C-ECU.