INSPECTION PROCEDURE 12: The PTC heater does not work <4N1>.
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COMMENTS ON TROUBLE SYMPTOM
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With the engine and blower motor being operated, if the PTC heater does not operate by setting the heater control to MAX HOT at the coolant temperature of 75 °C or lower, the PTC heater, PTC heater relay, heater controller assembly (A/C-ECU) or its circuit system may be faulty.
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- Malfunction of the PTC heater
- Malfunction of the PTC heater relay 1
- Malfunction of the PTC heater relay 2
- Malfunction of the PTC heater relay 3
- Malfunction of the ETACS-ECU
- Malfunction of the heater controller assembly (A/C-ECU)
- Damaged the wiring harness or connectors
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STEP 1. M.U.T.-III diagnosis code
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Check that the air conditioner has not set a diagnosis code.
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Q.
Is the diagnosis code set?
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 Carry out the diagnosis code procedures.
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 Go to Step 2.
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STEP 2. M.U.T.-III other system’s diagnosis code
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Check that the ETACS-ECU has not set a diagnosis code.
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Q.
Is the diagnosis code set?
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Carry out the diagnosis code procedures (Refer to GROUP 54A - ETACS-ECU  ).
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Go to Step 3.
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STEP 3. Check the PTC heater relay 1, 2 and 3.
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Refer to .
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Q.
Is the check result normal?
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Go to Step 4.
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Replace the PTC heater relay 1, 2 or 3.
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STEP 4. Measure the voltage at PTC heater connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Connect the HTR1 terminal of the heater controller assembly (A/C-ECU) connector to body earth.
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(4)Voltage between PTC heater connector terminal No.2 and body earth.
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 5.
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STEP 5. Measure the voltage at PTC heater relay 1 connector.
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(1)Remove the relay, and measure at the relay box side.
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(2)Voltage between terminal No.2 and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 7.
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Go to Step 6.
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STEP 6. Check of open circuit in power supply line between PTC heater relay 1 connector and fusible link
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 7. Measure the voltage at PTC heater relay 1 connector.
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(1)Remove the relay, and measure at the relay box side.
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(3)Voltage between terminal No.1 and body earth.
OK: System voltage
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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 of open circuit in IG11 line between PTC heater relay 1 connector and ETACS-ECU connector
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Prior to the wiring harness inspection, check intermediate connector and joint connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 9. Check of open circuit in power supply line between PTC heater relay 1 connector and PTC heater connector
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Q.
Is the check result normal?
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Go to Step 10.
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Repair the connector(s) or wiring harness.
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STEP 10. Check of open circuit in HTR1 line between PTC heater relay 1 connector and heater controller assembly (A/C-ECU) connector
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Prior to the wiring harness inspection, check intermediate connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 11. Measure the voltage at PTC heater connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Connect the HTR2 terminal of the heater controller assembly (A/C-ECU) connector to body earth.
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(4)Voltage between PTC heater connector terminal No.3 and body earth.
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 12.
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STEP 12. Measure the voltage at PTC heater relay 2 connector.
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(1)Remove the relay, and measure at the relay box side.
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(2)Voltage between terminal No.2 and body earth.
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 of open circuit in power supply line between PTC heater relay 2 connector and fusible link
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 14. Measure the voltage at PTC heater relay 2 connector.
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(1)Remove the relay, and measure at the relay box side.
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(3)Voltage between terminal No.1 and body earth.
OK: System voltage
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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 of open circuit in IG11 line between PTC heater relay 2 connector and ETACS-ECU connector
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Prior to the wiring harness inspection, check intermediate connector and joint connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 16. Check of open circuit in power supply line between PTC heater relay 2 connector and PTC heater connector
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Q.
Is the check result normal?
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Go to Step 17.
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Repair the connector(s) or wiring harness.
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STEP 17. Check of open circuit in HTR2 line between PTC heater relay 2 connector and heater controller assembly (A/C-ECU) connector
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Prior to the wiring harness inspection, check intermediate connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 18. Measure the voltage at PTC heater connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Connect the HTR3 terminal of the heater controller assembly (A/C-ECU) connector to body earth.
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(4)Voltage between PTC heater connector terminal No.1 and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 25.
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Go to Step 19.
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STEP 19. Measure the voltage at PTC heater relay 3 connector.
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(1)Remove the relay, and measure at the relay box side.
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(2)Voltage between terminal No.3 and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 21.
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Go to Step 20.
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STEP 20. Check of open circuit in power supply line between PTC heater relay 3 connector and fusible link
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 21. Measure the voltage at PTC heater relay 3 connector.
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(1)Remove the relay, and measure at the relay box side.
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(3)Voltage between terminal No.2 and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 23.
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Go to Step 22.
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STEP 22. Check of open circuit in IG11 line between PTC heater relay 3 connector and ETACS-ECU connector
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Prior to the wiring harness inspection, check intermediate connector and joint connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 23. Check of open circuit in power supply line between PTC heater relay 3 connector and PTC heater connector
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Q.
Is the check result normal?
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Go to Step 24.
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Repair the connector(s) or wiring harness.
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STEP 24. Check of open circuit in HTR3 line between PTC heater relay 3 connector and heater controller assembly (A/C-ECU) connector
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Prior to the wiring harness inspection, check intermediate connector, and repair if necessary.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the connector(s) or wiring harness.
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STEP 25. Resistance measurement at PTC heater connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Continuity between terminal No.1, 2 and body earth.
OK: Continuity (2Ω or less)
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Q.
Is the check result normal?
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Go to Step 27.
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Go to Step 26.
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STEP 26. Check of open circuit in earth line between PTC heater connector and body earth
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).
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Repair the wiring harness.
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STEP 27. Check the PTC heater.
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Refer to .
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Q.
Is the check result normal?
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Replace the heater controller assembly (A/C-ECU).
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Replace the PTC heater (Refer to ).
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