Oven
F04
The F04 error code on a Siemens oven indicates a fault with the oven’s temperature sensor (NTC probe), meaning the appliance cannot accurately read or regulate its internal temperature. It’s a moderate fault — your oven will likely stop heating entirely as a safety precaution, but it is not dangerous.
What does this error mean?
The F04 code tells you the oven’s control board has detected an abnormal signal from the NTC (Negative Temperature Coefficient) temperature sensor — the probe that monitors the cavity temperature during cooking. This could mean the sensor is reading too high, too low, or sending no signal at all. Because the oven cannot safely control its own heat, it shuts down the heating elements to prevent overheating or fire risk.
Est. repair cost
£15–£35 DIY (NTC sensor part only) or £80–£160 for a professional repair including labour
🔍 Likely causes
🛠️ Step-by-step fix
Power cycle the oven: switch it off at the wall socket (or trip the circuit breaker), wait 5 minutes, then restore power. This clears temporary electronic glitches and costs nothing.
Check the oven vent and fan area: make sure the oven’s cooling vents (usually at the top rear or top front trim) are not blocked by foil, baking trays, or built-up grease. Clear any obstructions and run the oven again.
Inspect the NTC sensor probe: the sensor is usually a small metal rod mounted on the inside rear wall of the oven cavity, held by one or two screws. With the oven unplugged, check that it is securely screwed in place and that the wiring connector at the back is firmly seated. Re-seat the connector if it looks loose.
Test the NTC sensor resistance (multimeter required): unplug the sensor connector and use a multimeter set to resistance (Ω). At room temperature (~20°C), a healthy Siemens NTC sensor typically reads around 4,000–6,000 ohms. A reading of 0 (short circuit) or OL (open circuit/infinite) confirms a faulty sensor — replace it.
Replace the NTC temperature sensor: genuine or compatible Siemens NTC sensors for most models cost £15–£35 from UK suppliers such as eSpares or 4ourhouse. The part number is stamped on the sensor body or found via your model number (on the oven door frame). Fitting involves removing two screws and swapping the connector — no specialist tools needed.
If the fault persists after a confirmed good sensor and clean wiring, do not attempt to repair or replace the main PCB yourself — contact a qualified appliance engineer, as PCB replacement requires safe electrical testing.
📞 When to call a professional
Call a qualified appliance engineer if the error returns after replacing the NTC sensor, or if you find burnt, melted, or severely corroded wiring inside the oven cavity. Tell the engineer: ‘My Siemens oven is showing an F04 error code — I believe it’s the NTC temperature sensor circuit, and I’ve already ruled out a simple sensor replacement.’ This saves diagnostic time and labour cost.
⚖️ Repair or replace?
A professional repair for an F04 fault — covering diagnosis, NTC sensor replacement, or PCB work — typically costs £80–£160 with a UK appliance engineer. If your Siemens oven is under 8 years old, repair is almost always the right call; Siemens built-in ovens retail from £400–£900, making repair excellent value. If the oven is over 10 years old and the PCB has failed, replacement becomes more economical.