Oven
F12
The F12 error code on a Bosch oven indicates a fault with the oven’s temperature sensor (NTC sensor) or its associated wiring. It’s a moderately serious fault — your oven will typically stop heating safely until it’s resolved.
What does this error mean?
F12 signals that the oven’s control board has detected an abnormal reading from the NTC (Negative Temperature Coefficient) temperature sensor, which monitors the internal oven cavity temperature. Either the sensor is reading a temperature outside its expected range, or the signal isn’t reaching the control board at all. This prevents the oven from regulating heat correctly, so it shuts down as a safety precaution.
Est. repair cost
£15–£35 DIY sensor replacement; £80–£200 for a professional repair including call-out
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 – Hard reset: Switch the oven off at the wall socket (or trip the circuit breaker), wait 5 minutes, then power it back on. If F12 clears and doesn’t return, it was a temporary glitch.
Step 2 – Check for obvious spillages: If food or liquid has overflowed near the back wall of the oven cavity, clean it thoroughly once the oven is cool. Debris around the sensor probe can cause false readings.
Step 3 – Locate the NTC sensor: In most Bosch single and double ovens, the NTC sensor is a small metal probe mounted on the back interior wall of the oven cavity, held by one or two screws. It is accessible without opening any sealed electrical panels.
Step 4 – Inspect the sensor and its connector: With the oven fully unplugged, unscrew the sensor and carefully pull it forward to expose the wiring connector. Check for visible corrosion, burn marks, or a loose plug. Reseat the connector firmly.
Step 5 – Test or replace the NTC sensor: NTC sensors for Bosch ovens typically cost £15–£35 online (search your full model number, found inside the oven door frame). A working sensor should show approximately 990–1100 ohms resistance at room temperature — testable with a cheap multimeter. If the reading is open circuit (OL) or zero, replace the sensor.
Step 6 – If replacing the sensor doesn’t fix F12: Stop here and call a professional. The fault likely lies with the wiring harness or the PCB control board, both of which require disassembly of sealed electrical components.
📞 When to call a professional
Call a qualified appliance engineer if the F12 error returns after a reset and sensor replacement, or if you find burnt or melted wiring inside the oven. Tell the engineer: ‘My Bosch oven is showing an F12 fault — I believe it’s an NTC temperature sensor or PCB issue.’ If your oven is a gas-electric range with gas hobs, ensure the engineer is also Gas Safe registered before they work on the appliance.
⚖️ Repair or replace?
A professional repair for F12 — covering call-out, diagnosis, and a new NTC sensor or PCB — typically costs £80–£200 in the UK. If your Bosch oven is under 8 years old, repair is almost always worthwhile; Bosch ovens retail from £400–£900+. If it’s over 10 years old and the PCB needs replacing (£120–£180 for the part alone), replacing the oven becomes the more economical choice.