Inspection Procedure 10

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:

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

TROUBLESHOOTING HINTS
- Malformation 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-16 for damage.

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

YES: Go to Step 2.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning 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 10 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES: Go to Step 4.

NO: Go to Step 3.







STEP 3. Check the wiring harness between A/C-ECU connector C-16 (terminal 10) and the ignition switch (IG2).

NOTE: Also check junction block connectors C-214 and C-211. If junction block connectors C-214 or C-211 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-16 (terminal 10) 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. Check that the air conditioning works normally.

STEP 4. 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 12 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 air conditioning works normally.

NO: Go to Step 5.







STEP 5. Check the wiring harness between A/C-ECU connector C-16 (terminal 12) and the ground.

NOTE: Also check joint connector (3) C-06. If joint connector (3) C-06 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-16 (terminal 12) and the ground in good condition?

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

NO: Repair the wiring harness. Check that the air conditioning works normally.