Inspection Procedure 1
SYMPTOM PROCEDURESINSPECTION PROCEDURE 1: Malfunction of the A/C-ECU Power SupplySystem.
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. Refer to 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 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 in 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. Refer to How to Use Troubleshooting/Inspection Service Points - 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. Refer to 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 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 28) 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-20 (terminal 28) 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 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. Refer to How to Use Troubleshooting/Inspection Service Points - 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. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Replace the A/C-ECU.