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Error code reference

Miele Washer Error Code F4045

Resistance of NTC 1 greater than highest permissible figure (open circuit).

Miele codesMiele washer codes

Resistance of NTC 1 greater than highest permissible figure (open circuit).

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What F4045 means on a Miele washer

The F4045 error code on a Miele washer indicates that the resistance value measured from NTC 1 (the primary temperature sensor) has exceeded the highest permissible threshold, which the control board interprets as an open circuit condition. NTC stands for Negative Temperature Coefficient, meaning the sensor's resistance decreases as temperature increases. When the control detects resistance that is too high, it indicates the sensor circuit is broken rather than reading a legitimate temperature, and the machine halts operation to prevent uncontrolled or unmonitored heating.

NTC 1 is typically positioned to monitor the water temperature inside the wash drum or heating circuit. The control board sends a small reference voltage through the sensor and reads the resulting resistance to calculate temperature. An open circuit can result from a broken sensor element, a disconnected or corroded wiring harness connector, or a damaged wire somewhere along the circuit between the sensor and the control board. In some cases, the sensor itself fails internally, causing the resistance to rise infinitely rather than tracking with temperature.

Diagnosing this fault correctly requires a multimeter to measure resistance across the NTC 1 sensor terminals directly. A healthy NTC sensor at room temperature typically reads within a defined resistance range specific to the sensor model. A reading of infinite resistance (OL on a digital multimeter) confirms an open circuit within the sensor itself. If the sensor reads correctly when tested in isolation, the fault lies in the wiring harness or the connector pins between the sensor and the control board.

Source: manufacturer service documentation.

Common causes of F4045

  1. 01

    Failed NTC 1 temperature sensor

    Part replacement

    The sensor element itself has broken internally, causing the resistance to read as infinite (open circuit). Testing the sensor directly with a multimeter will show no continuity or an OL reading across its terminals.

  2. 02

    Disconnected or loose wiring connector

    Wiring / connection

    The connector linking NTC 1 to the wiring harness may have come loose, particularly after vibration over time or during previous service work. Inspecting and reseating the connector at both the sensor and control board ends may resolve the fault.

  3. 03

    Corroded or damaged connector pins

    Wiring / connection

    Moisture inside the machine can cause corrosion at the sensor connector pins, increasing resistance in the circuit to the point of an open circuit condition. Visually inspect the pins for green or white oxidation and clean or replace the connector as needed.

  4. 04

    Broken or chafed wiring in the harness

    Wiring / connection

    A wire in the circuit between NTC 1 and the control board may have broken internally or chafed through its insulation against a sharp edge, severing continuity. A continuity test along the full length of the harness will identify the break.

  5. 05

    Faulty control board

    Part replacement

    In rare cases, the control board's input circuit for NTC 1 may have failed, causing it to misread a functional sensor as open circuit. This should only be considered after the sensor and wiring have been confirmed good with direct testing.

See the test procedure for each cause

Frequently asked questions about F4045

What does F4045 mean on a Miele washer?
F4045 means the resistance measured from NTC 1, the primary water temperature sensor, is higher than the maximum permissible value, which the control board interprets as an open circuit. This tells the machine that the sensor circuit is broken and temperature cannot be reliably monitored. The washer will stop operation until the fault is corrected to prevent unsafe heating conditions.
Can I fix the F4045 error myself?
Some causes of F4045 are accessible to a confident DIYer, particularly inspecting and reseating wiring connectors or cleaning corroded pins. Testing the NTC 1 sensor with a multimeter is straightforward if you can access the sensor. However, replacing the sensor or diagnosing a control board fault typically requires disassembly of the machine and is better suited to a qualified appliance technician.
Is it safe to use my Miele washer while F4045 is showing?
No, you should not attempt to operate the washer while F4045 is active. The error indicates the temperature sensor circuit is open, meaning the machine cannot monitor water temperature. Running a heated wash cycle without functional temperature sensing creates a risk of water overheating, and the machine is designed to halt operation for this reason.
Will resetting the washer clear the F4045 error?
A power reset may temporarily clear the error display, but the fault will return immediately once the control board checks the NTC 1 sensor circuit again, which happens at startup or during the wash cycle. The underlying sensor or wiring problem must be diagnosed and repaired before the error will clear permanently.
How much does it cost to repair a Miele washer F4045 error?
Repair costs vary depending on the root cause. If only a connector needs cleaning or reseating, cost is minimal. Replacing the NTC 1 temperature sensor typically involves parts costs in the range of $20 to $80 depending on the specific model. If the control board is at fault, parts and labor combined can range from $200 to $500 or more. A technician diagnosis fee is typically charged separately to identify the exact cause.

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