Inspection Procedure 2

INSPECTION PROCEDURE 2: Malfunction of the A/C-ECU Power Supply System.

A/C-ECU Power Supply Circuit:

TECHNICAL DESCRIPTION (COMMENT)
The A/C-ECU power system may be defective if the air conditioning, 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 Tool:
- MB991223: Test Harness Set

STEP 1. Check A/C-ECU connector C-109 for loose,corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is A/C-ECU connector C-109 in good condition?

YES: Go to Step 2.

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




STEP 2. Measure the voltage at A/C-ECU connector C-109.

1. Disconnect A/C-ECU connector C-109 and measure the voltage at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 15 and ground.
- The measured value should be approximately 2 volts (battery positive voltage).

Q: Is the measured voltage approximately 12 volts?

YES: Go to Step 5.

NO: Go to Step 3.

STEP 3. Check ETACS-ECU connector C-317 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is ETACS-ECU connector C-317 in good condition?

YES: Go to Step 4.

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

STEP 4. Check the wiring harness between A/C-ECU connector C-109 (terminal 15) and ETACS-ECU connector C-317 (terminal 5).

Q: Is the wiring harness between A/C-ECU connector C-109(terminal 15) and ETACS-ECU connector C-317 (terminal 5) 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. Check that the A/C works normally.

STEP 5. Measure the voltage at A/C-ECU connector C-109.

1. Disconnect A/C-ECU connector C-109 and measure the voltage at the harness side.




2. Measure the voltage between terminal 13 and ground.
- The measured value should be approximately 2 volts (battery positive voltage).

Q: Is the measured voltage approximately 12 V?

YES: Go to Step 7.

NO: Go to Step 6.

STEP 6. Check the wiring harness between A/C-ECU connector C-109 (terminal 13) and the FUSIBLE LINK (36).

NOTE: Also check ETACS-ECU connector C-317 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If ETACS-ECU connector C-317 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-109 (terminal 13) and the FUSIBLE LINK (36) 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. Check that the A/C works normally.

STEP 7. Measure the resistance at A/C-ECU connector C-109.

1. Disconnect A/C-ECU connector C-109, and measure at the wiring harness side.




2. Measure the resistance between terminal 14 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 8.

STEP 8. Check the wiring harness between A/C-ECU connector C-109 (terminal 14) and the ground.

Q: Is the wiring harness between A/C-ECU connector C-109 (terminal 14) 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. Check that the A/C works normally.