High Lockout
AC on Worcester Bosch Greenstar 25HE

Your boiler's main internal computer has lost communication with one of its electronic parts, meaning it cannot operate until the connection is restored.

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 central control board stops receiving signals from its internal electronic module. The most common cause is a loose connection in the wiring harness or a critical failure of the Printed Circuit Board (PCB) itself. If these sensors and modules cannot talk to each other, the boiler shuts 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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