INSPECTION PROCEDURE 5: The blower air volume cannot be changed <Front side>
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COMMENTS ON TROUBLE SYMPTOM
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If air volume cannot be adjusted by using the blower control, the heater controller assembly (A/C-ECU) or the power transistor may be faulty.
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- Malfunction of the power transistor
- Damaged wiring harness or connectors
- Malfunction of the heater controller assembly (A/C-ECU)
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STEP 1. M.U.T.-III CAN bus diagnostics.
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting  ).
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STEP 2. M.U.T.-III diagnosis code.
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Check that the diagnosis code related to the air conditioner is not set.
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Q.
Is the diagnosis code set?
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Carry out the diagnosis code procedures (Refer to ).
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Go to Step 3.
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STEP 3. Check the data list below on the M.U.T.-III.
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All the following items in the data list should be normal.
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Item No.69: Front blower fan (Target)
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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Go to Step 4.
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STEP 4. Voltage measurement at power transistor connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Turn the ignition switch to the "ON" position.
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(3)Voltage between terminal 2 and body earth.
OK: System voltage
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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 5.
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STEP 5. Check open circuit in blower motor line between blower motor and power transistor.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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Repair or replace the connector(s) or wiring harness.
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STEP 6. Resistance measurement at the power transistor connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Continuity between terminal 1 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 7.
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Go to Step 8.
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STEP 7. Check open circuit power transistor earth line between power transistor 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 Cope with Intermittent Malfunction ).
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Repair or replace the connector(s) or wiring harness.
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STEP 8. Voltage measurement at heater controller (A/C-ECU) connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Turn the ignition switch to the "ON" position.
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(3)Voltage between BASE terminal and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 10.
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Go to Step 9.
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STEP 9. Check open circuit power transistor and blower motor line between power transistor connector and heater controller (A/C-ECU) connector BASE terminal.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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Repair or replace the connector(s) or wiring harness.
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STEP 10. Replace the power transistor (Refer to ) and recheck the trouble symptom.
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Check that the blower motor operates normally.
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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Replace the heater controller assembly (A/C-ECU) (Refer to ).
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