BoilerFaultCodesYour boiler has lost communication with a small internal component that tells the main computer what specific model it is.
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 boiler's internal computer loses contact with a small identification chip called a code plug. This usually happens because the plug has vibrated loose over time, developed poor electrical contact, or the main control board itself has suffered an internal hardware failure. Without this component, the boiler cannot verify which specific model it is and shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like b1 — no call-out fees, no surprises.
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