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Error code reference

Thermador Oven Error Code F31

Upper oven sensor open.

Thermador codesThermador oven codes

Upper oven sensor open.

First step from the service manual

Check sensor wiring at pin header P3 on relay board; when sensor opens, F-31 code will appear.

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 oven

The F31 error code on a Thermador oven indicates that the upper oven temperature sensor circuit is open. An open circuit means the sensor or its wiring is no longer completing the electrical loop that allows the oven control board to read temperature. The control board continuously monitors the resistance signal from the temperature sensor (typically an RTD or resistance temperature detector), and when that signal is lost entirely, the board registers the fault and displays F31 to prevent unsafe uncontrolled heating.

The first place to inspect is the sensor wiring connection at pin header P3 on the relay board. A loose, corroded, or damaged connection at this header can interrupt the circuit just as effectively as a failed sensor itself. The wiring harness running from the sensor through the oven cavity wall to the relay board is also exposed to repeated heat cycling, which can cause wire insulation to crack, connectors to loosen, or terminal pins to back out of their housings over time.

If the wiring and connectors at P3 check out visually and electrically, the upper oven sensor itself is the next likely culprit. A properly functioning oven temperature sensor will show a measurable resistance value at room temperature. An open sensor will show infinite or no resistance on a multimeter. Replacing the sensor is a straightforward repair in most cases, but confirming the wiring integrity first can save unnecessary parts costs.

Source: manufacturer service documentation.

Common causes of F31

  1. 01

    Loose or disconnected wiring at relay board header P3

    Wiring / connection

    The sensor wire connector at pin header P3 on the relay board can work loose over time due to vibration and heat cycling. Inspect the connector for loose pins, backing, or corrosion and reseat it firmly.

  2. 02

    Failed upper oven temperature sensor

    Part replacement

    The sensor itself can fail internally, creating an open circuit. Use a multimeter to check resistance across the sensor leads. An open reading (no continuity or infinite resistance) confirms sensor failure.

  3. 03

    Damaged sensor wiring harness

    Part replacement

    The wiring between the sensor and the relay board runs through or near the oven cavity and can crack, burn, or break due to repeated heat exposure. Visually inspect the full length of the harness for damaged insulation or broken wires.

  4. 04

    Corroded or oxidized connector terminals

    Wiring / connection

    Terminal pins at the P3 header or at the sensor connector can develop corrosion that increases resistance to the point of an open circuit. Inspect terminals for discoloration or buildup and clean or replace as needed.

  5. 05

    Faulty relay board

    Part replacement

    If the sensor and all wiring test correctly but F31 persists, the relay board itself may have a defect at the P3 input circuit. This is the least common cause and should only be considered after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F31

What does F31 mean on a Thermador oven?
F31 means the upper oven temperature sensor circuit is open, meaning the oven control system has lost its electrical connection to the sensor that monitors oven temperature. Without a valid temperature reading, the oven cannot operate safely. The fault is detected through the relay board at pin header P3, which is the starting point for diagnosis.
Can I fix F31 on my Thermador oven myself?
Some causes of F31 are DIY-friendly, particularly reseating a loose connector at pin header P3 on the relay board or replacing the upper oven temperature sensor. Testing the sensor with a multimeter and inspecting the wiring harness for visible damage are reasonable first steps for a knowledgeable homeowner. However, if the relay board itself needs replacement, a qualified technician is recommended.
Will resetting the oven clear the F31 code?
Resetting the oven by cycling the power may temporarily clear the F31 code, but if the underlying cause is not corrected, the fault will return as soon as the oven attempts to operate again. A reset is useful for confirming whether the fault is intermittent, such as from a loose connection, but it is not a repair. The root cause in the sensor circuit must be addressed for the code to stay cleared.
Is it safe to use my Thermador oven when F31 is displayed?
No, you should not attempt to use the oven while F31 is active. The code indicates the oven has no reliable temperature feedback from the upper cavity sensor, which means the heating system cannot regulate temperature properly. Operating the oven in this condition could result in overheating or uncontrolled heating cycles.
How much does it cost to repair a Thermador oven F31 error?
If the repair only involves reseating a loose connector, there may be no parts cost at all, though a service call fee will apply if you use a technician. Replacing the upper oven temperature sensor typically costs between $50 and $150 for the part, plus labor. A relay board replacement, if needed, can range from $150 to $400 or more for the part alone, making professional diagnosis important before committing to that repair.

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