High Lockout
E12 on Viessmann Vitodens 100-W

Your boiler's main control computer and the front display screen have stopped talking to each other, meaning the unit cannot function.

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

Control unit fault. Communication error with the display.

What causes this fault?

This fault occurs when the internal communication link between the boiler's main brain and the front control panel is broken. It is usually caused by a loose internal connection cable, a short circuit on one of the circuit boards, or moisture ingress affecting the sensitive electronics.

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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Related fault codes

E11View →E13View →F0View →

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