Oven
F03
The F03 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. It’s a moderately serious fault — the oven will typically stop heating to prevent damage or a fire risk.
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 inside the oven cavity. This sensor tells the oven how hot it is so it can maintain the correct temperature. Without a reliable reading, the oven shuts down the heating element as a safety precaution.
Est. repair cost
£15–£40 DIY (NTC sensor part only); £80–£150 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. A one-off glitch can trigger F03 and a reset clears it.
Check the oven is not overheated: if you’ve been using it on a high setting for a long time, let it cool for 30 minutes before resetting — the sensor may have tripped due to genuine excess heat.
Locate the NTC sensor: it’s usually a small metal probe mounted on the back wall inside the oven cavity, held in place by one or two screws. Inspect it visually for any obvious burn marks, cracks, or physical damage.
Check the sensor connector: with the oven fully unplugged from the mains, gently pull out the sensor connector (accessible from inside the cavity or behind the back panel) and reseat it firmly. Corroded pins can be carefully cleaned with electrical contact cleaner.
Test the sensor resistance: using a multimeter set to resistance (Ω), a healthy Bosch NTC oven sensor reads approximately 990–1010Ω at room temperature (around 20°C). A reading outside this range confirms a faulty sensor — replacement parts cost £15–£40 and are widely available for Bosch models.
Replace the NTC sensor: unscrew the old sensor, disconnect the wiring, and fit the new part in reverse order. This is a straightforward DIY task on most Bosch ovens and takes under 20 minutes — no specialist tools required beyond a Torx or Phillips screwdriver.
📞 When to call a professional
If replacing the NTC sensor does not clear the F03 code, the fault likely lies with the wiring harness or the main control board (PCB) — both of which require a qualified appliance engineer to diagnose and replace safely. Call an engineer and tell them: ‘My Bosch oven is showing F03, I’ve already replaced the NTC temperature sensor and the fault persists.’ This helps them arrive prepared with the right parts.
⚖️ Repair or replace?
A professional repair for an F03 fault — covering sensor replacement or PCB diagnosis — typically costs £80–£150 including labour in the UK. If your Bosch oven is under 8 years old and otherwise reliable, repair is almost always the better value. For ovens over 10 years old or where the PCB has failed (repair cost £150–£250+), replacing with a new mid-range Bosch oven (£400–£700) is worth serious consideration.