BoilerFaultCodesYour boiler's main control chip is either loose or has failed, which means the computer can't identify the specific model to operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Keyed plug not detected.
What causes this fault?
This fault occurs when the small memory chip, known as a code plug, becomes loose or fails, meaning the boiler's main computer can no longer identify which model it is controlling. Without this vital identity information, the boiler shuts down immediately as a safety precaution because it doesn't know its own operating limits. The most common cause is either a vibration-related loose connection or an internal electronic failure within the plug or the main circuit board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like b1 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 25HE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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