BoilerFaultCodesYour boiler's internal computer or control module has developed a fault and can no longer communicate with the rest of the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
What causes this fault?
This fault occurs when the boiler's internal computer chips lose the ability to talk to each other, often due to a physical failure in the circuitry. The most common reason is that the Heat Control Module has worn out or developed a loose connection, meaning the boiler can no longer safely manage the heating process. In some cases, a power surge or general age-related degradation of the main control board is the root cause.
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 EH258 — no call-out fees, no surprises.
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