Oven
F03
The F03 error code on a Siemens oven indicates a fault with the oven temperature sensor (NTC sensor), meaning the appliance cannot reliably monitor or regulate its internal temperature. This fault will prevent the oven from heating safely and should not be ignored.
What does this error mean?
F03 signals that the oven’s control board has detected an open circuit or out-of-range reading from the NTC (Negative Temperature Coefficient) temperature sensor, which is the probe responsible for measuring the oven cavity temperature. Without an accurate temperature reading, the oven’s electronics cannot control heating elements correctly. Siemens builds in this fault code as a safety cutout to prevent overheating or underheating your food — and more importantly, to protect the appliance from damage.
Est. repair cost
DIY NTC sensor replacement: £15–£35 for the part. Professional repair (sensor or wiring): £80–£150. PCB replacement by engineer: £150–£250+.
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 – Hard reset first: Switch the oven off at the wall socket (or trip the circuit breaker), leave it for 5–10 minutes, then restore power. If F03 clears and does not return, monitor the oven closely over the next few uses — a one-off glitch can occasionally trigger the code.
Step 2 – Check your manual: Confirm that F03 is listed as a temperature sensor fault in your specific Siemens model’s documentation. Model numbers are typically on a label inside the oven door frame. This rules out a misread code.
Step 3 – Inspect the sensor visually (safe, no tools required beyond removing oven shelves): The NTC sensor is usually a thin metal probe mounted on the back wall of the oven cavity. Look for obvious burn marks, physical damage, or a loose connection at the probe’s base. Do not attempt to open the back panel or access internal wiring — stop here if any internal access is needed.
Step 4 – Test or replace the NTC sensor: If you’re comfortable using a multimeter, the NTC sensor should read approximately 1,000 ohms at room temperature (20°C). A reading of zero or infinity confirms a failed sensor. Replacement NTC sensors for Siemens ovens are widely available online for £15–£35 and are a straightforward swap — unplug the old sensor, plug in the new one. Always isolate the oven from the mains before doing this.
Step 5 – Check the wiring connector: Once the oven is isolated from power, gently remove and reseat the sensor’s wiring connector. Look for corrosion (green or white residue on pins) and clean lightly with electrical contact cleaner if needed. Reconnect, restore power, and check if F03 has cleared.
Step 6 – If the error persists after sensor replacement: The fault likely lies with the main control board (PCB). Do not attempt to repair or replace the PCB yourself — call a qualified appliance engineer at this stage.
📞 When to call a professional
Call a qualified appliance repair engineer if F03 persists after a hard reset and NTC sensor replacement, or if you are not confident working safely with electrical appliances. When you call, tell the engineer: ‘My Siemens oven is showing error code F03, which I understand is a temperature sensor fault — I’ve already tried a reset and visually inspected the sensor.’ This helps them arrive prepared with the right parts and saves you on call-out time.
⚖️ Repair or replace?
A professional repair for an F03 fault — typically NTC sensor replacement or a PCB swap — costs £80–£180 including labour in the UK. If your Siemens oven is under 8 years old, repair is almost always worthwhile given that a comparable built-in Siemens oven costs £500–£1,200 new. If the oven is over 10 years old and the PCB is at fault (£120–£200+ for the part alone), replacement becomes the more economical choice.