Oven
F31
The F31 error code on a Bosch oven indicates a fault with the oven temperature sensor (NTC sensor), meaning the oven cannot accurately read or regulate its internal temperature. This fault will prevent the oven from heating safely and needs to be resolved before normal use can resume.
What does this error mean?
F31 signals that the oven’s NTC (Negative Temperature Coefficient) temperature sensor is sending a reading that is either out of range, open-circuit, or implausible — essentially, the oven’s brain cannot trust the temperature data it’s receiving. Bosch ovens use this sensor to regulate heat precisely; without a reliable reading, the appliance locks out heating as a safety precaution. This is not a catastrophic failure — in most cases it points to a faulty or disconnected sensor rather than a damaged control board.
Est. repair cost
£15–£40 DIY sensor replacement; £80–£150 professional sensor repair; £150–£300 if PCB replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 – Reset the oven: Switch the oven off at the wall socket, leave it unpowered for 5 minutes, then switch back on. If F31 clears, monitor it over the next few uses. A one-off glitch can trigger a false error.
Step 2 – Locate the NTC sensor: With the oven cold and unplugged, open the oven door and look for a small metal probe, usually mounted on the rear interior wall of the cavity. It’s typically held by one or two screws.
Step 3 – Check the sensor for visible damage: Inspect the probe and its wiring for signs of burning, corrosion, or physical damage. If the probe looks cracked or the wire insulation is melted, the sensor needs replacing.
Step 4 – Check the wiring connector: Trace the sensor wire to its connector (usually accessible by removing the back panel of the oven — unplug first). Firmly reseat the connector. If the terminals look burnt or corroded, clean gently with electrical contact cleaner.
Step 5 – Test the sensor resistance with a multimeter: A healthy Bosch NTC oven sensor typically reads around 1,000 ohms (1kΩ) at room temperature (20°C). A reading of zero (short) or infinite (open circuit) confirms a faulty sensor. Replacement sensors cost £15–£40 and are readily available by part number from your oven’s model label.
Step 6 – Replace the NTC sensor: Unscrew the old sensor, disconnect the wiring, and fit the new one in reverse order. Plug the oven back in and run a test heat cycle to confirm the error has cleared. If F31 returns after a confirmed sensor replacement, do not attempt to replace the PCB yourself — call a qualified engineer.
📞 When to call a professional
Call a qualified appliance engineer if the error persists after replacing the NTC sensor, as the fault likely lies with the oven’s main control board (PCB) — a job that involves working inside live electrical components and is not safe for DIY. Tell the engineer you’ve already replaced the NTC sensor and the resistance tested correctly, so they can focus diagnostics on the PCB and wiring loom. Also call immediately if you notice any burning smell, scorch marks, or tripped circuit breakers alongside the F31 code.
⚖️ Repair or replace?
A professional repair (sensor replacement plus callout) typically costs £80–£150 in the UK; a PCB replacement can push this to £150–£300 depending on the Bosch model. If your oven is under 8 years old, repair is almost always worth it — Bosch built-in ovens retail from £350 upwards and a sensor fix is straightforward. If the oven is over 10 years old and requires a PCB, replacement is the better financial decision.