High Lockout
F.49 on Vaillant ecoTEC Pro / ecoTEC Plus

Your boiler has lost communication between its internal computer and parts like the thermostat due to an electrical connection issue.

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

eBUS error – possible short circuit

What causes this fault?

This fault occurs when the boiler's internal communication system, known as the eBUS, suffers an electrical failure or short circuit. It is often caused by moisture getting into the wiring, a loose connection to the thermostat, or even two wires touching where they shouldn't. This prevents the control board from receiving instructions, causing the system to shut down for safety.

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

F.70View →F.22View →

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