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INSPECTION PROCEDURE 8: A/C-ECU power supply system
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
If the auto A/C controller assembly (A/C-ECU) is not energized, the power supply or ground system to the ECU may be defective.
 
 
 
PROBABLE CAUSES
  • Malfunction of the A/C-ECU.
  • Damaged wiring harness or connectors
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnostic trouble code check.
Check that the ETACS-ECU has not set a diagnostic trouble code.
Is the diagnostic trouble code set?
Carry out the diagnostic trouble code procedures (Refer to GROUP 54A, ETACS-ECU ).
Go to Step 2.
 
STEP 2. Measure the voltage at the auto A/C controller assembly (A/C-ECU) connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Voltage between terminal No. 20 and body ground.
OK: System voltage
Is the check result normal?
Go to Step 3.
Go to Step 4.
 
STEP 3. Check open circuit in IG2 line between IG (2) relay and A/C controller assembly (A/C-ECU) connector.
noteBefore the wiring harness check, check the junction block connector.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 4. Measure the resistance at the auto A/C controller assembly (A/C-ECU) connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between terminal No. 19 and body ground.
OK: Continuity exists (2 Ω or less)
Is the check result normal?
Replace the auto A/C controller assembly (A/C-ECU).
Go to Step 5.
 
STEP 5. Check open circuit in E line between auto A/C controller assembly (A/C-ECU) connector and body ground.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the wiring harness.