Oven
F34
The F34 error code on a Bosch oven indicates a fault with the oven’s temperature sensor (NTC sensor) or the associated wiring — it’s a moderately serious fault that will prevent the oven from heating safely until resolved.
What does this error mean?
Bosch ovens use an NTC (negative temperature coefficient) sensor to monitor internal cavity temperature in real time. When the control board detects that the sensor is reading outside its expected resistance range — or not responding at all — it throws the F34 code and locks out the heating elements as a safety precaution. This means your oven has lost confidence in its ability to regulate temperature accurately.
Est. repair cost
£10–£25 DIY sensor replacement; £80–£140 professional sensor repair; £150–£280 if control board replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
Power cycle the oven: switch it off at the wall socket or isolate it at the fuse board for 5 minutes, then switch back on. This clears temporary electronic faults and is always worth trying first.
Check for error recurrence: run the oven to a standard temperature (e.g. 180°C). If F34 returns within a few minutes, a hardware fault is confirmed and you’ll need to investigate further.
Locate the NTC sensor: on most Bosch built-in ovens, it’s a small metal probe (roughly 3–4cm long) mounted on the back interior wall of the oven cavity. Consult your model’s manual if you can’t see it.
Inspect the sensor for visible damage: look for burn marks, corrosion, or physical breakage. If the probe is visibly damaged, it needs replacing — Bosch NTC sensors are widely available online for £10–£25, specific to your model number.
Check the connector: pull the oven out from its housing (after isolating the power), trace the sensor wire to its connector, and check for loose, burnt, or corroded pins. Reseating a loose connector occasionally resolves F34.
If the sensor and wiring look intact, do not attempt to open the control board housing yourself — this requires a qualified appliance engineer to test and replace the PCB safely.
📞 When to call a professional
Call a qualified appliance engineer if the error persists after a reset and you cannot identify an obvious sensor or wiring issue, or if you suspect the control board (PCB) is at fault. When you call, quote the model number (found on the oven door frame sticker) and tell the engineer you have an F34 fault — they’ll likely bring an NTC sensor and diagnostic tools as standard.
⚖️ Repair or replace?
An NTC sensor replacement by a professional typically costs £80–£140 all-in for labour and parts — a very reasonable repair on an oven under 8 years old. If the control board needs replacing, costs rise to £150–£280, at which point you should weigh this against the oven’s age and original value. For ovens over 10 years old where the PCB has failed, replacement is often the more cost-effective option.