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Error code reference

Thermador Range Error Code F31

Upper oven sensor open (or single oven temperature sensor failure).

Thermador codesThermador range codes

Upper oven sensor open (or single oven temperature sensor failure).

First step from the service manual

Check all connections; check resistance of upper oven sensor (approximately 1080 ohms at room temperature); check solder joints in header P3/P4; if sensor is OK replace power/relay board.

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

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What F31 means on a Thermador range

The F31 error code on a Thermador range indicates that the upper oven temperature sensor circuit has opened, meaning the control board is detecting either no signal or an out-of-range signal from the sensor. In a dual-oven configuration, this refers specifically to the upper cavity sensor. In a single-oven model, the same code flags the only oven temperature sensor present. The temperature sensor is a resistance temperature detector (RTD) that should measure approximately 1080 ohms at room temperature. When the circuit reads an open condition, the control interprets this as a failed or disconnected sensor and shuts down oven operation to prevent uncontrolled heating.

The most common causes include a physically failed RTD sensor, a loose or corroded wiring harness connector, or broken solder joints at header P3 or P4 on the power and relay board. The header connections are a known weak point because thermal cycling over years of use can cause solder joints to crack, interrupting the sensor signal even when the sensor itself tests within spec. Diagnosing this code requires a multimeter reading at the sensor leads. A reading significantly above or below 1080 ohms at room temperature confirms sensor failure. A correct resistance reading at the sensor but an F31 code at the board points toward wiring, connector, or solder joint issues.

If the sensor resistance is correct and all wiring connections are secure and undamaged, the fault lies in the power and relay board itself. The board processes the sensor input signal, and an internal board failure can produce a false open reading even with a functioning sensor circuit. Replacing the power and relay board is the recommended next step after confirming sensor and wiring integrity.

Source: manufacturer service documentation.

Common causes of F31

  1. 01

    Failed upper oven temperature sensor (RTD)

    Part replacement

    The RTD sensor itself has failed and is no longer producing a readable resistance signal. A measurement at the sensor terminals that deviates significantly from approximately 1080 ohms at room temperature confirms the sensor needs replacement.

  2. 02

    Loose or disconnected wiring harness connector

    Wiring / connection

    Vibration and heat cycles can loosen the connector between the oven sensor and the control board, breaking the circuit. Inspect all connectors in the sensor wiring path for corrosion, bent pins, or incomplete seating.

  3. 03

    Cracked solder joints at header P3 or P4 on the power and relay board

    Wiring / connection

    Thermal cycling over time can cause solder joints at the P3 or P4 header to crack, interrupting the sensor signal at the board level. Visually inspect these joints under magnification for hairline fractures or lifted pads.

  4. 04

    Damaged sensor wiring

    Part replacement

    The wiring between the sensor and the control board can become pinched, burned, or broken, creating an open circuit. Trace the sensor wire along its full path looking for visible damage or melted insulation.

  5. 05

    Failed power and relay board

    Part replacement

    If the sensor measures correctly at approximately 1080 ohms and all connections are intact, the power and relay board may have an internal fault causing a false open reading. Board replacement is the indicated repair at this point.

See the test procedure for each cause

Frequently asked questions about F31

What does F31 mean on a Thermador range?
F31 indicates that the upper oven temperature sensor circuit is reading as open, meaning the control board cannot detect a valid signal from the RTD sensor. The oven will not heat while this fault is active because the control has no way to regulate temperature safely. The sensor should read approximately 1080 ohms at room temperature when functioning correctly. The fault can originate at the sensor itself, the wiring, the header connections on the power and relay board, or the board itself.
Can I fix F31 on my Thermador range myself?
A knowledgeable DIYer can perform the initial diagnostics by checking connector seating and measuring the sensor resistance with a multimeter. If the sensor resistance is far from 1080 ohms at room temperature, the sensor is a straightforward part to replace. However, inspecting solder joints at headers P3 and P4 or replacing the power and relay board involves working with internal board components, which is better suited to a technician with appliance repair experience.
Is it safe to use my Thermador range while F31 is displayed?
The range displays F31 specifically because it cannot monitor oven temperature, which means it cannot prevent overheating. Using the oven in this condition is not safe and the oven heating function is typically disabled by the control when this fault is active. Surface burners on a gas or electric range may still operate, but the oven should not be used until the fault is resolved.
How much does it cost to repair a Thermador F31 error?
Repair costs vary depending on which component has failed. A replacement oven temperature sensor typically costs in the range of $25 to $75 for the part alone. If the power and relay board requires replacement, parts can range from $150 to $400 or more depending on the specific model. Adding professional labor will increase the total, generally bringing a full repair to somewhere between $150 and $600 depending on the fault and your location.
Will resetting my Thermador range clear the F31 error code?
Resetting the range by disconnecting power for a few minutes may temporarily clear the F31 code, but the error will return if the underlying fault is still present. The control will detect the open sensor circuit again as soon as it attempts to read oven temperature. A reset is useful for confirming the fault is persistent rather than a one-time glitch, but it does not substitute for diagnosing and repairing the faulty sensor, wiring, or board.

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