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-14 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is A/C-ECU connector C-14 in good condition?

YES: Go to Step 2.

NO: Repair or replace the connector. Refer to Harness Connector Inspection.

STEP 2. Check the wiring harness for open circuit.




1. Disconnect A/C-ECU connector C-14 and the battery harness, and measure at the wiring harness side.




2. Measure the resistance between A/C-ECU connector C-14 terminal 8 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-14 (terminal 8) 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.

Q: Is the wiring harness between A/C-ECU connector C-14 (terminal 8) and the battery in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Repair the wiring harness.

STEP 4. Check the wiring harness for open circuit.




1. Disconnect A/C-ECU connector C-14 and ignition switch connector, and measure the resistance at the wiring harness side.




2. Measure the resistance between A/C-ECU connector C-14 terminal 7 and ignition switch connector.

OK: Less than 10 ohms

Q: Is the check result normal?

YES: Go to Step 6.

NO: Go to Step 5.







STEP 5. Check the wiring harness between A/C-ECU connector C-14 (terminal 7) and the ignition switch (IG2).

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.

Q: Is the wiring harness between A/C-ECU connector C-14 (terminal 7) and the ignition switch (IG2) in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Repair the wiring harness.

STEP 6. Check the wiring harness for open circuit.




1. Disconnect A/C-ECU connector C-14, and measure the resistance at the wiring harness side.




2. Measure the resistance between A/C-ECU connector C-14 terminal 2 and ground.

OK: Less than 10 ohms

Q: Is the check result normal?

YES: Go to Step 8.

NO: Go to Step 7.




STEP 7. Check the wiring harness between A/C-ECU connector C-14 (terminal 2) and ground.

Q: Is the wiring harness between A/C-ECU connector C-14 (terminal 16) and ground in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Repair the wiring harness.

STEP 8. 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. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.

NO: Replace the heater control.