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INSPECTION PROCEDURE 5: Malfunction of Power Supply Circuit System
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
AWC-ECU power supply circuit, ground circuit, or AWC-ECU may have a problem.
 
 
PROBABLE CAUSES
  • Malfunction of ETACS-ECU
  • Damaged wiring harness and connectors
  • Malfunction of AWC-ECU

 
 
DIAGNOSIS
Required Special Tools:
  • MB992006: Extra fine probe
STEP 1. Check of the fuse No.13 and No.15.
Visually check for open circuit in the fuse No.13, No.15.
Is the check result normal?
Go to Step 7.
Go to Step 2.
 
STEP 2. Check the wiring harness between electronic control coupling solenoid connector and AWC-ECU connector terminal SOL+.
Check the power supply line for short circuit.
Is the check result normal?
Go to Step 3.
Repair the wiring harness wire and/or connector(s), and then replace fuse No.13.
 
STEP 3. Check the wiring harness between electronic control coupling solenoid connector and AWC-ECU connector terminal SOL-.
Check the ground line for short to the power supply.
Is the check result normal?
Go to Step 4.
Repair the wiring harness wire and/or connector(s), and then replace fuse No.13.
 
STEP 4. Check of the electronic control coupling solenoid
Refer to .
Is the check result normal?
Go to Step 5.
Repair the wiring harness wire and/or connector(s), and then replace fuse No.13.
 
STEP 5. Check the wiring harness between ETACS-ECU connector and AWC-ECU connector terminal AWDF
Check the power supply for short circuit.
Is the check result normal?
Go to Step 6.
Repair the wiring harness wire and/or connector(s), and then replace fuse No.13.
 
STEP 6. Check the wiring harness between ETACS-ECU connector and AWC-ECU connector terminal IG16
Check the power supply for short circuit.
Is the check result normal?
Replace the fuse Nos.13 and 15.
Repair the wiring harness wire and/or connector(s), and then replace fuse No.15.
 
STEP 7. Voltage measurement at ETACS-ECU connector
Disconnect the connector, and measure the voltage between terminal +B1 and body ground at the wiring harness side.
OK: System voltage
Is the check result normal?
Go to Step 9.
Go to Step 8.
 
STEP 8. Check the wiring harness between ETACS-ECU connector terminal +B1 and fusible link No.40
Check the power supply line for open circuit or short circuit.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Repair the defective connector or the wiring harness.
 
STEP 9. Voltage measurement at the AWC-ECU connector
(1) Disconnect the connector, and measure the voltage between terminal IG1 and body ground at the wiring harness side.
(2) Turn the ignition switch to the ON position.
OK: System voltage
Is the check result normal?
Go to Step 11.
Go to Step 10.
 
STEP 10. Check the wiring harness between ETACS-ECU connector terminal IG16 and AWC-ECU connector terminal IG1.
Check the power supply line for open circuit or short circuit.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Repair the defective connector or the wiring harness.
 
STEP 11. Voltage measurement at the AWC-ECU connector
Disconnect the connector, and measure the voltage between terminal BATT and body ground at the wiring harness side.
OK: System voltage
Is the check result normal?
Go to Step 13.
Go to Step 12.
 
STEP 12. Check the wiring harness between ETACS-ECU connector and AWC-ECU connector terminal BATT.
Check the power supply line for open circuit.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Repair the defective connector or the wiring harness.
 
STEP 13. Measure the resistance at the AWC-ECU connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between AWC-ECU connector terminal GND1 and body ground.
OK: Continuity exists (2 Ω or less)
Is the check result normal?
Go to Step 15.
Go to Step 14.
 
STEP 14. Check the wiring harness between AWC-ECU connector terminal GND1 and body ground.
Check the ground line for open circuit.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Repair the defective connector or the wiring harness.
 
STEP 15. Retest the system.
Does the malfunction occur again?
Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ).Then go to Step 16.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
 
STEP 16. Retest the system.
Does the malfunction occur again?
Replace the AWC-ECU (Refer to ).
This diagnosis is complete.