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Error code reference

Thermador Range Error Code 04

WFK 2401 washer

Thermador codesThermador range codes

WFK 2401 washer: Overheating.

First step from the service manual

Check voltage to heater. If voltage is present when heater shouldn't be on, replace faulty control module.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What 04 means on a Thermador range

Error code 04 on this Thermador unit signals an overheating condition. This code is tied to the heating circuit, where the control module monitors the heater's operating state and temperature. When the system detects heat output beyond the expected range, or when the heater element is energized at a time when it should be off, the control module flags this fault to prevent damage to internal components and surrounding surfaces.

The primary diagnostic focus is the voltage supplied to the heater. A technician should measure voltage at the heater terminals during the fault condition. If voltage is present when the heater should not be active, this points directly to a control module that is failing to cut power to the heating circuit at the correct time. A malfunctioning relay or output driver within the control module can hold the heater circuit closed unintentionally, causing continuous or unregulated heat output.

Beyond control module failure, technicians should also consider the possibility of a faulty temperature sensor providing incorrect feedback to the control board, which could cause the board to misread the thermal state of the system. Wiring issues, such as shorts within the heater circuit, can also contribute to unexpected voltage presence. The diagnostic sequence should begin with voltage measurement at the heater before condemning any single component, as this reading directly separates a wiring or relay fault from a sensor or thermistor issue.

Source: manufacturer service documentation.

Common causes of 04

  1. 01

    Faulty control module

    Part replacement

    The control module may have a failed relay or output driver that keeps voltage supplied to the heater even when the heater should be off. This is confirmed by measuring voltage at the heater terminals during a period when the heater should not be active.

  2. 02

    Failed temperature sensor

    Part replacement

    A defective temperature sensor can send incorrect readings to the control board, causing it to mismanage the heating cycle and trigger an overheating fault. Resistance testing of the sensor can help identify an out-of-range reading.

  3. 03

    Short circuit in the heater wiring

    Wiring / connection

    A wiring short within the heater circuit can cause unintended voltage to appear at the heater terminals. Inspect the wiring harness for damaged insulation, pinched wires, or burnt connectors.

  4. 04

    Heater element stuck energized

    Part replacement

    In some cases the heater element itself can have an internal fault that causes it to draw current outside of normal control parameters. Check resistance across the element terminals to identify an open or shorted condition.

See the test procedure for each cause

Frequently asked questions about 04

What does 04 mean on a Thermador range?
Error code 04 indicates an overheating condition in the appliance's heating circuit. The control system has detected that the heater is operating outside of its expected parameters, either running too hot or staying energized when it should be off. This fault is designed to protect the appliance from heat-related damage. A technician should check voltage at the heater and inspect the control module.
Can I fix error code 04 on my Thermador range myself?
The first step, checking for voltage at the heater, requires electrical testing equipment and knowledge of safe practices around live circuits. If voltage is confirmed to be present when the heater should be off, the control module will need to be replaced, which typically requires disassembly and familiarity with appliance wiring. This repair is best handled by a qualified technician unless you have hands-on experience with appliance electrical systems.
Is error code 04 on a Thermador range a safety concern?
Yes, an overheating fault is a safety-related condition. If the heater is being supplied with voltage when it should be off, it can cause the appliance to overheat without any user command. You should stop using the appliance until the fault has been diagnosed and resolved to avoid the risk of damage or fire.
How much does it cost to repair error code 04 on a Thermador range?
Repair costs depend on the root cause. If the control module is at fault, parts alone can range from roughly $150 to $400 or more depending on the model, with labor adding additional cost. If the issue is a wiring short or a failed temperature sensor, the total repair cost would generally be lower. Getting a diagnostic estimate from a technician before authorizing any parts replacement is advisable.
Will resetting my Thermador range clear error code 04?
Resetting the appliance by cutting power may temporarily clear the fault display, but it will not fix the underlying problem. If the control module or heater circuit is faulty, the error code 04 will return once the appliance is powered on and the fault condition is detected again. A proper diagnosis of the heater voltage and control module is needed to resolve the issue permanently.

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