Inspection Procedure 6: The power supply circuit system fails
COMMENTS ON TROUBLE SYMPTOM
The 4WD-ECU or the power supply or earth circuit to the ECU may have a problem.
PROBABLE CAUSES
- Malfunction of ETACS-ECU
- Damaged harness wires and connectors
- Malfunction of 4WD-ECU
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STEP 1. Fuse No.13, No.15 check
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Visually check that fuses No. 13 and 15 are not blown.
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Q.
Is the check result normal?
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 Go to Step 4.
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 Go to Step 2.
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STEP 2. Check the SOL (+) wire between the electronic-controlled coupling solenoid connector and the 4WD-ECU connector 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 harness or connector. Then go to Step 19.
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STEP 3. Check the SOL (-) wire between the electronic-controlled coupling solenoid connector and the 4WD-ECU connector for short to 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 or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 4. Check the electronic-controlled coupling solenoid.
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Refer to  .
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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 or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 5. Check the 4WDF line between the ETACS-ECU connector and the 4WD-ECU connector for short circuit.
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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 or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 6. Check the IG16 line between the ETACS-ECU connector and the 4WD-ECU connector for short circuit.
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Q.
Is the check result normal?
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Replace the fuses No. 13 and 15.Then go to Step 7.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 7. Voltage measurement at ETACS-ECU connector (+B1 terminal)
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Disconnect the connector, and measure the voltage between the ETACS-ECU connector (+B1 terminal) and earth at the wiring harness side.
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Q.
Is the check result normal?
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Go to Step 9.
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Go to Step 8.
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STEP 8. Check the +B1 line between the ETACS-ECU connector and fusible link No.2 for open or short circuit.
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Q.
Is the check result normal?
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Go to Step 19.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 9. Voltage measurement at ETACS-ECU connector (IG1 terminal)
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(1)Disconnect the connector, and measure the voltage between the ETACS-ECU connector (IG1 terminal) and 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 11.
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Go to Step 10.
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STEP 10. Check the IG1 line between the ETACS-ECU connector and J/C (2) for open or short circuit.
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Q.
Is the check result normal?
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Go to Step 19.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 11. Voltage measurement at the 4WD-ECU connector (4WDF terminal)
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Disconnect the connector, and measure the voltage between the 4WD-ECU connector (4WDF terminal) and earth at the wiring harness side.
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Q.
Is the check result normal?
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Go to Step 13.
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Go to Step 12.
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STEP 12. Check the 4WDF line between the ETACS-ECU connector and the 4WD-ECU connector for open circuit.
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Q.
Is the check result normal?
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Go to Step 19.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 13. Voltage measurement at the 4WD-ECU connector (IG16 terminal)
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(1)Disconnect the connector, and measure the voltage between the 4WD-ECU connector (IG16 terminal) and 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 15.
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Go to Step 14.
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STEP 14. Check the IG16 line between the ETACS-ECU connector and the 4WD-ECU connector for open circuit.
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Q.
Is the check result normal?
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Go to Step 19.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 15. Resistance measurement at the 4WD-ECU connector (GND1 terminal)
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Disconnect the connector, and measure the resistance between the 4WD-ECU connector (GND1 terminal) and earth at the wiring harness side.
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OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 17.
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Go to Step 16.
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STEP 16. Check the GND1 line between the 4WD-ECU connector and body earth for open circuit.
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Q.
Is the check result normal?
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Go to Step 19.
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Repair the wiring harness or the connector, and replace fuse No. 13. Then go to Step 19.
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STEP 17. Retest the system.
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Q.
Is the check result normal?
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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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Replace the ETACS-ECU. (Refer to GROUP 54A - ETACS-ECU .) Then go to Step 18.
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STEP 18. Retest the system.
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Q.
Is the check result normal?
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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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Replace 4WD-ECU (Refer to ). Then go to Step 19 .
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STEP 19. Retest the system.
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Q.
Is the check result normal?
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This diagnosis is complete.
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Return to Step 1.
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