Inspection Procedure 1

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













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. Harness Connector Inspection.

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 2 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 in Harness Connector Inspection Harness Connector Inspection.

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. How to Cope With Intermittent Malfunctions.

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. Harness Connector Inspection.

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 2 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 in Harness Connector Inspection Harness Connector Inspection.

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. How to Cope With Intermittent Malfunctions.

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 2 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. How to Cope With Intermittent Malfunctions.

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. How to Cope With Intermittent Malfunctions.
NO Replace the A/C-ECU.