Oven
F04
The F04 error code on a Bosch oven indicates a fault with the oven’s temperature sensor (NTC sensor), meaning the appliance cannot accurately read or regulate its internal temperature. It’s a moderately serious fault — your oven will likely stop heating or refuse to start until it’s resolved.
What does this error mean?
Bosch ovens use an NTC (Negative Temperature Coefficient) sensor to monitor the internal cavity temperature and relay that information to the control board. When the control board receives a signal that falls outside the expected range — either no signal, a short circuit, or an open circuit in the sensor — it triggers the F04 code and shuts down heating as a safety precaution. In plain terms: your oven doesn’t know how hot it is, so it refuses to operate.
Est. repair cost
£15–£40 DIY (NTC sensor part only); £80–£150 professional repair; £150–£250+ if PCB replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
1. Power cycle the oven: Switch it off at the wall socket or trip the circuit breaker, wait 5 minutes, then restore power. A one-off electronic glitch can trigger F04 — a hard reset clears it at no cost.
2. Check the oven manual: Confirm F04 is listed as a temperature sensor fault in your specific Bosch model’s documentation. Codes can vary slightly between series (e.g. Serie 4 vs Serie 8).
3. Inspect the sensor and its wiring (oven unplugged and cooled): The NTC sensor is typically a small probe mounted on the back wall inside the oven cavity. Look for visible burn marks, damaged insulation on the wire, or a disconnected plug. Do not probe with tools while the oven is powered.
4. Test the sensor with a multimeter (unplugged): Disconnect the sensor plug and measure resistance across the two terminals. At room temperature (~20°C), a healthy Bosch NTC sensor typically reads around 4,000–6,000 ohms. A reading of zero (short) or infinite (open circuit) confirms a failed sensor.
5. Replace the NTC sensor: Bosch oven NTC sensors are widely available from UK parts suppliers (e.g. eSpares, 4ourhouse) for £15–£40. The part usually clips or screws in and has a simple two-wire connector — a confident DIYer can swap it in under 30 minutes with the oven unplugged.
6. If the error persists after sensor replacement: The control board (PCB) may be at fault. Stop DIY at this point — PCB replacement involves handling mains-voltage components and should be done by a qualified appliance engineer.
📞 When to call a professional
Call a qualified appliance engineer if the F04 code returns after you’ve replaced the NTC sensor, or if you find burned or melted wiring inside the oven cavity — this suggests deeper electrical damage that needs professional diagnosis. When booking, tell the engineer: ‘My Bosch oven is showing an F04 error code, which I understand relates to the NTC temperature sensor — I’ve already replaced the sensor but the fault persists.’
⚖️ Repair or replace?
A professional repair for an F04 fault — covering diagnosis, sensor replacement, and labour — typically costs £80–£150 in the UK. If the PCB is also faulty, expect £150–£250+. As a rule of thumb, if your oven is over 8–10 years old and repair costs exceed 50% of a comparable new oven (budget Bosch built-in ovens start at around £250–£350), replacement is the smarter investment. For ovens under 6 years old in otherwise good condition, repair is almost always worth it.