High Lockout
AC on Worcester Bosch Greenstar 12i System

Your boiler's main control board has lost communication with an internal plug-in module or sensor, meaning it cannot currently operate.

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

Module not detected.

What causes this fault?

This fault occurs when the boiler's main control board loses its connection to a specific internal electronic component or plug-in module. The most common reason is a loose wiring connection or a hardware failure within the circuit board that prevents the various parts of the boiler from talking to each other. Because the control board can no longer 'see' all its necessary components, it chooses to shut down as a safety precaution.

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

A1View →C6View →E9View →

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