01 High

Atag 01 Fault Code

The Atag 01 fault code means: your boiler has detected an external safety signal, such as a fire alarm or frost thermostat, which has instructed the unit to shut down for safety reasons.. It appears on 6 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: External safety contact cut out
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 01 fault code

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

Source

Atag 01 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 7 July 2026