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

Typical repair cost for the Baxi E.04 – .04 fault is £90-180 including labour.

E.04 – .04 High

Baxi E.04 – .04 Fault Code

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

Your boiler has detected an issue with the sensor that monitors exhaust gases, and it has locked the system down as a safety precaution.

Also written as E0404 — same fault.

The Baxi E.04 – .04 fault code means: your boiler has detected an issue with the sensor that monitors exhaust gases, and it has locked the system down as a safety precaution.. It appears on 24 Baxi models in our database.

Technical description: Permanent fault. Flue temperature sensor short-circuited, sensor not or badly connected, bad connection or sensor fault.

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

This fault occurs when the boiler's internal safety system detects an irregular electrical signal from the sensor monitoring the heat of the exhaust gases. The most common reason is that the sensor has developed a physical defect or the wiring connecting it to the main control board has come loose or been damaged. Because the boiler can no longer accurately monitor flue temperatures, it shuts down to prevent any risk of overheating.

Typical repair cost £90-180 (including labour)

Engineer required

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

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

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

Source

Baxi E.04 – .04 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