E04 High

Atag E04 Fault Code

The Atag E04 fault code means: your boiler has detected an issue with the temperature of the water returning to the unit, suggesting the system is struggling to circulate water correctly or a sensor is misreading.. It appears on 3 Atag models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: °C return water temperature T2
Typical repair cost £120-250 (including labour)

Engineer required

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

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Atag models that show the E04 fault code

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

Source

Atag E04 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

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