Oven
F31
The F31 error code on a Siemens oven indicates a fault with the oven temperature sensor (NTC sensor), meaning the appliance cannot correctly monitor or regulate heat. It’s a moderately serious fault — the oven will typically refuse to operate until it’s resolved.
What does this error mean?
F31 signals that the oven’s control board has detected an abnormal reading from the NTC (Negative Temperature Coefficient) temperature sensor, usually an open circuit or a reading that falls outside the expected resistance range. In plain terms, the oven doesn’t know what temperature it’s at, so it shuts down as a safety precaution. This is an electrical fault, not a gas issue, and in many cases it can be diagnosed and fixed without a specialist callout.
Est. repair cost
DIY sensor replacement: £15–£35 for the part. Professional repair: £80–£150 (sensor) or £150–£280 (control board), including callout and labour.
🔍 Likely causes
🛠️ Step-by-step fix
Reset the oven first: switch it off at the wall socket or consumer unit, wait 5 minutes, then power it back on. If F31 clears, monitor the oven through a full heating cycle before trusting it again.
Inspect the sensor connector: pull the oven away from the wall (unplug first), remove the back panel if accessible, and check the NTC sensor connector is firmly seated. Reseat it if loose.
Visually inspect the sensor wiring: look for any visibly burnt, frayed, or pinched cables running from the sensor (usually located at the back wall or top of the oven cavity). Do not touch or repair internal wiring yourself — if damaged, call a professional.
Test the NTC sensor resistance: if you own a multimeter, disconnect the sensor and measure resistance across its terminals. A healthy Siemens NTC sensor typically reads around 1,000 ohms (1kΩ) at room temperature (~25°C). A reading of zero (short) or infinite resistance (open circuit) confirms a failed sensor.
Replace the NTC sensor if faulty: Siemens NTC sensors are widely available online for £15–£35. Ensure you have the exact model number (found on the rating plate inside the oven door frame) before ordering. Replacement involves unplugging the sensor from its connector and removing one or two screws — no soldering required.
If the new sensor does not clear F31, stop DIY work. The control board is likely at fault, which requires a qualified appliance engineer to diagnose and replace safely.
📞 When to call a professional
Call a qualified appliance engineer if: the error persists after replacing the NTC sensor, the wiring harness appears burnt or damaged, or you’re not confident using a multimeter. When booking, tell the engineer you have a Siemens oven showing error code F31 and that you suspect an NTC temperature sensor or control board fault — this helps them bring the right parts and reduces callout time.
⚖️ Repair or replace?
A professional repair (sensor replacement) typically costs £80–£150 including labour and parts; a control board replacement rises to £150–£280 depending on the model. If your oven is under 8 years old, repair is almost always worth it — Siemens built-in ovens retail from £400 upwards. If it’s over 10 years old and the control board needs replacing, weigh repair cost against a new appliance, especially if other components are aging.