INSPECTION PROCEDURE
5: Malfunction of Power Supply Circuit System
COMMENTS ON TROUBLE SYMPTOM
AWC-ECU power supply circuit, earth circuit, or AWC-ECU may have a problem.
PROBABLE CAUSES
- Malfunction of ETACS-ECU
- Damaged wiring harness and connectors
- Malfunction of AWC-ECU
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STEP 1. Check of the fuse No.13 and No.15.
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Visually check for open circuit in the fuse No.13, No.15.
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Q.
Is the check result normal?
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 Go to Step 6.
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 Go to Step 2.
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STEP 2. Check the wiring harness between electronic control coupling
solenoid (front) connector and AWC-ECU connector terminal FSL+.
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Check the power supply line for short circuit.
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 3. Check the wiring harness between electronic control coupling
solenoid (front) connector and AWC-ECU connector terminal FSL-.
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Check the earth line for short to the power supply.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 4. Check the wiring harness between electronic control coupling
solenoid (centre) connector and AWC-ECU connector terminal SOL+.
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Check the power supply line for short circuit.
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 5. Check the wiring harness between electronic control coupling
solenoid (centre) connector and AWC-ECU connector terminal SOL-.
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Check the earth line for short to the power supply.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 6. Check of the electronic control coupling solenoid (front)
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Refer to  .
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Q.
Is the check result normal?
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Go to Step 7.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 7. Check of the electronic control coupling solenoid (centre)
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Refer to GROUP 27C - On-vehicle Service.
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Q.
Is the check result normal?
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Go to Step 8.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 8. Check the wiring harness between ETACS-ECU connector and AWC-ECU
connector terminal 4WDF
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Check the power supply for short circuit.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.13. Then go to Step 22.
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STEP 9. Check the wiring harness between ETACS-ECU connector and AWC-ECU
connector terminal IG16
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Check the power supply for short circuit.
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Q.
Is the check result normal?
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Replace the fuse Nos.13 and 15. Then go to Step 10.
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Repair the wiring harness wire and/or connector(s), and then replace
fuse No.15. Then go to Step 22.
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STEP 10. Voltage measurement at ETACS-ECU connector
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Disconnect the connector, and measure the voltage between terminal +B1 and body
earth at the wiring harness side.
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Q.
Is the check result normal?
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Go to Step 12.
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Go to Step 11.
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STEP 11. Check the wiring harness between ETACS-ECU connector terminal +B1
and fusible link No.2
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Check the power supply line for open circuit or short circuit.
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Q.
Is the check result normal?
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Go to Step 22.
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Repair the defective connector or the wiring harness. Then go to Step 22.
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STEP 12. Voltage measurement at the ETACS-ECU connector
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(1)Disconnect the connector, and measure the voltage between terminal IG1 and body
earth at the wiring harness side.
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(2)Turn the ignition switch to the ON position.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 14.
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Go to Step 13.
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STEP 13. Check the wiring harness between ETACS-ECU connector terminal
IG1 and J/C(2).
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Check the power supply line for open circuit or short circuit.
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Q.
Is the check result normal?
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Go to Step 22.
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Repair the defective connector or the wiring harness. Then go to Step 22.
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STEP 14. Voltage measurement at the AWC-ECU connector
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Disconnect the connector, and measure the voltage between terminal 4WDF and body earth
at the wiring harness side.
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Q.
Is the check result normal?
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Go to Step 16.
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Go to Step 15.
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STEP 15. Check the wiring harness between ETACS-ECU connector and
AWC-ECU connector terminal 4WDF.
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Check the power supply line for open circuit.
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Q.
Is the check result normal?
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Go to Step 22.
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Repair the defective connector or the wiring harness. Then go to Step 22.
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STEP 16. Voltage measurement at the AWC-ECU connector
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(1)Disconnect the connector, and measure the voltage between terminal IG16 and body
earth at the wiring harness side.
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(2)Turn the ignition switch to the ON position.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 18.
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Go to Step 17.
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STEP 17. Check the wiring harness between ETACS-ECU connector terminal
IG16 and AWC-ECU connector terminal IG16.
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Check the power supply line for open circuit.
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Q.
Is the check result normal?
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Go to Step 22.
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Repair the defective connector or the wiring harness. Then go to Step 22.
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STEP 18. Measure the resistance at the AWC-ECU connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Resistance between AWC-ECU connector terminal GND1 and body earth.
OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 20.
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Go to Step 19.
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STEP 19. Check the wiring harness between AWC-ECU connector terminal
GND1 and body earth.
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Check the earth line for open circuit.
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Q.
Is the check result normal?
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Go to Step 22.
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Repair the defective connector or the wiring harness. Then go to Step 22.
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STEP 20. Retest the system.
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Q.
Does the malfunction occur again?
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Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU).Then go to Step
21.
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to Use Troubleshooting/How to Cope with Intermittent Malfunctions).
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STEP 21. Retest the system.
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Q.
Does the malfunction occur again?
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Replace the AWC-ECU (Refer to ). Then go to
Step 22.
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to Use Troubleshooting/How to Cope with Intermittent Malfunctions).
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STEP 22. Retest the system.
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Q.
Does the malfunction occur again?
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Return to Step 1.
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This diagnosis is complete.
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