High Lockout
0D on Viessmann Vitodens 333-F

Your boiler has detected an internal communication error and has shut itself down as a safety precaution.

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

Burner control switches to lockout

What causes this fault?

This fault occurs when the boiler's internal computer loses the ability to communicate with the components that control the flame. The most common reason is a hardware failure within the burner control unit or a loose electrical connection that prevents the system from safely managing the ignition process.

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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