How much does it cost to fix Baxi error code E.04 – .12?

Typical repair cost for the Baxi E.04 – .12 fault is £120-350 including labour.

E.04 – .12 High

Baxi E.04 – .12 Fault Code

Q: What does the Baxi E.04 – .12 fault code mean?

Your boiler has detected a flame signal when there shouldn't be one, or it is running too hot to operate safely.

Also written as E0412 — same fault.

The Baxi E.04 – .12 fault code means: your boiler has detected a flame signal when there shouldn't be one, or it is running too hot to operate safely.. It appears on 24 Baxi models in our database.

Technical description: Permanent fault. False flame signal, short-term fluctuation of the mains, ionization current present even though there is no flame, the burner remains very hot (CO2 too high) or defective gas/air unit.

What causes the Baxi E.04 – .12 fault?

This fault occurs when the boiler's internal sensors detect a flame after the heating cycle has finished or identify that the burner assembly is dangerously overheating. The most common reason is a sensor incorrectly reporting a signal due to moisture or carbon buildup, or a gas valve that is failing to close fully and let the burner cool down.

Typical repair cost £120-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Baxi models that show the E.04 – .12 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Baxi E.04 – .12 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026