High Lockout
b1 on Worcester Bosch Greenstar 12i System

Your boiler's main internal computer cannot find its unique identity chip, causing the system to stop working for safety.

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

Code plug not detected.

What causes this fault?

This fault occurs when the boiler's control board loses communication with a small, specialized data chip inside the unit. The most common reason is that the chip has worked loose due to minor vibrations over time, or the internal circuitry of the Printed Circuit Board has failed, preventing it from reading the chip's identity.

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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