BoilerFaultCodesYour boiler's internal computer chip is missing or not making a proper connection, which means the system doesn't know which settings to use and has stopped working.
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. Code plug version, connection and sitting. If OK replace control board.
What causes this fault?
This fault occurs when the small memory chip that tells the boiler how to operate is either loose, damaged, or has been removed. It is often caused by vibrations over time loosening the connection, or a failure in the main control board's ability to read the chip's data.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like b1 — no call-out fees, no surprises.
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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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