High Lockout
H.01 – .00 on Baxi 200 Combi (range)

Your boiler has lost its internal connection to the main gas control unit, meaning it cannot safely manage the fuel it needs to fire up.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Loss of communication between gas valve and boiler board. Possible fault in air/gas unit or loose connection to gas valve.

What causes this fault?

This fault occurs when the boiler's internal computer is no longer able to talk to the electronic gas valve, which is the component that controls the fuel supply. The most common reason is a loose or damaged wiring connection between these two parts, or an electronic failure within the valve itself that prevents it from responding to commands.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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