BoilerFaultCodesYour boiler's internal computer has encountered a critical electronic malfunction and can no longer control the heating system safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Internal failure - electronic
What causes this fault?
This fault occurs when the boiler's main control board suffers a hardware failure, meaning the electronic components can no longer communicate with each other correctly. The most common reason is age-related wear to the circuitry or a sudden electrical surge that has damaged the delicate microprocessors inside the unit.
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 403 — no call-out fees, no surprises.
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