High Lockout
B1 on Worcester Bosch Greenstar i

Your boiler's internal computer brain cannot find its identity chip, which prevents it from operating safely.

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: Code plug version, condition and fitting. If OK replace control board.

What causes this fault?

This fault occurs when the boiler's main control board loses communication with a small, specialized chip called a coding plug that contains the unit's unique settings. The most common reason is that the plug has vibrated loose or become faulty, but it can also happen if moisture or a power surge has damaged the circuitry on the main control board.

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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