How much does it cost to fix Baxi error code E.04 – .03?

Typical repair cost for the Baxi E.04 – .03 fault is £120-£350 including labour.

E.04 – .03 High

Baxi E.04 – .03 Fault Code

Q: What does the Baxi E.04 – .03 fault code mean?

Your boiler has shut down because water is not moving through the system properly, causing it to overheat.

Also written as E0403 — same fault.

The Baxi E.04 – .03 fault code means: your boiler has shut down because water is not moving through the system properly, causing it to overheat.. It appears on 24 Baxi models in our database.

Technical description: Permanent fault. Critical flow temperature reached, non-existent or insufficient circulation.

What causes the Baxi E.04 – .03 fault?

This fault occurs when the water inside your boiler gets too hot too quickly because it isn't moving through the pipes as it should. The most common reasons are a failed internal pump that can no longer push the water, or a blockage such as a build-up of sludge or debris within the system.

This issue is frequently seen when heating is first turned on in autumn, as internal pump parts can seize up after being inactive during the summer months.

Typical repair cost £120-£350 (including labour)

DIY fix possible

Check if your radiator valves are openEnsure the boiler pressure gauge is between 1 and 1.5 barCheck for frozen condensate pipes during cold weatherTry resetting the boiler using the selector switch

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 – .03 fault code

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

Source

Baxi E.04 – .03 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