BoilerFaultCodesYour boiler's computer memory chip is loose or missing, meaning the system doesn't know which model it is and has stopped working for safety.
Book a Gas Safe engineer within 24–48 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, removable chip called the code plug. It is usually caused by the plug vibrating loose over time or failing due to a hardware fault on the main circuit board. Without this chip, the boiler cannot verify which model it is or what safety settings to use, so it shuts down immediately.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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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 CDi Classic 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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