Trouble symptom
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Inspection procedure
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Reference pages or actions
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M.U.T.-III cannot communicate with electric power steering system <ECU power supply circuit system check>.
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1
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Electric power steering system warning display illuminates but diagnosis code is not stored.
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2
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The steering has become heavy, but the electric power steering warning display does not illuminate (This is normal, because the electric power steering is limiting assist operation).
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If the vehicle is driven under heavy load (e.g. consecutively turning the steering to full lock or severe cornering), the electric power steering motor drive circuit will become hot. In this case, the electric power steering system will limit assist operation by decreasing the motor current to avoid damage. In this case, the steering will become heavy, but the electric power steering warning lamp does not illuminate. If the circuit temperature reduces after a while, the assist operation will return to the normal level.
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Reproduce the steering operation, which your customer did. Check the M.U.T.-III data list item to No.A55 from No.A11, and confirm that the electric power steering system limited the assist operation (Refer to ). Note that this is not a failure.
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The steering has become heavy, but the electric power steering warning display does not illuminate (Power supply voltage assist fall).
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If the system voltage is lower than the rated value, motor rated output does not come out.
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3
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When the ignition switch is turned on, the system does not perform the bulb check for the electric power steering warning lamp (The electric power steering warning lamp does not illuminate until the engine is started).
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The ignition switch is turned to the ON position (within approximately 3 second) again immediately after it is turned to the LOCK (OFF) position, the electric power steering warning lamp does not illuminate.
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Replace the meter assembly (Refer to GROUP 54A - Combination Meter ).
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