Inspection Procedure 10

INSPECTION PROCEDURE 10: Malfunction of the A/C-ECU Power Supply System.


















TECHNICAL DESCRIPTION (COMMENT)

The A/C-ECU power system may be defective if the air conditioner, defogger, and outside/inside air selection damper motor all do not operate normally.

TROUBLESHOOTING HINTS

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

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check A/C-ECU connector C-16 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is A/C-ECU connector C-16 in good condition?

YES Go to Step 2.

NO Repair or replace the connector. Harness Connector Inspection.
Check that the A/C works normally.

STEP 2. Measure the voltage at A/C-ECU connector C-16.





(1)Disconnect A/C-ECU connector C-16 and measure the voltage at the harness side.
(2)Turn the ignition switch to the "ON" position.





(3)Measure the voltage between terminal 28 and ground.

- The measured value should be approximately 12 volts (battery positive voltage).

Q. Is the measured voltage approx. 12 volts?

YES Go to Step 4.

NO Go to Step 3.

STEP 3. Check the wiring harness between A/C-ECU connector C-16 (terminal 28) and the ignition switch (IG2).













NOTE:
Also check joint connector C-03, junction block connectors C-211 and C-215 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-03, junction block connector C-211 or C-215 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

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

Q. Is the wiring harness between A/C-ECU connector C-16 (terminal 28) and the ignition switch (IG2) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness. Check that the A/C works normally.

STEP 4. Measure the voltage at A/C-ECU connector C-16.





(1)Disconnect A/C-ECU connector C-16 and measure the voltage at the harness side.
(2)Turn the ignition switch to the "ACC" position.





(3)Measure the voltage between terminal 36 and ground.

- The measured value should be approximately 12 volts (battery positive voltage).

Q. Is the measured voltage approx. 12 volts?

YES Go to Step 6.

NO Go to Step 5.

STEP 5. Check the wiring harness between A/C-ECU connector C-16 (terminal 36) and the ignition switch (ACC).









NOTE:
Also check joint connector C-03 and intermediate connector C-29 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-03 or intermediate connector C-29 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

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

Q. Is the wiring harness between A/C-ECU connector C-16 (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. Check that the A/C works normally.

STEP 6. Measure the voltage at A/C-ECU connector C-15.





(1)Disconnect A/C-ECU connector C-15 and measure the voltage at the harness side.





(2)Measure the voltage between terminal 3 and ground.

- The measured value should be approximately 12 volts (battery positive voltage).

Q. Is the measured voltage approx. 12 volts?

YES Go to Step 8.

NO Go to Step 7.

STEP 7. Check the wiring harness between A/C-ECU connector C-15 (terminal 3) and the battery.









NOTE:
Also check joint connector C-01 and intermediate connector C-29 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-01 or intermediate connector C-29 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

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

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. Check that the A/C works normally.

STEP 8. Measure the resistance at A/C-ECU connector C-16.





(1)Disconnect A/C-ECU connector C-16, and measure at the wiring harness side.





(2)Measure the resistance between terminal 27 and ground.

- The measured value should be 2 ohms or less.

Q. Does the measured resistance value correspond with this range?

YES Replace the A/C-ECU, and check that the A/C works normally.

NO Go to Step 9.

STEP 9. Check the wiring harness between A/C-ECU connector C-16 (terminal 27) and the ground.





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

Q. Is the wiring harness between A/C-ECU connector C-16 (terminal 27) and ground in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions. check that the A/C works normally.

NO Repair the wiring harness. Check that the A/C works normally.