BoilerFaultCodesYour boiler has switched itself off because it has become too hot inside, likely due to water not flowing correctly or a faulty internal sensor.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Maximum flue gas temperature reached. No circulation or sensor fault.
What causes this fault?
This fault occurs when the internal temperature of the boiler rises dangerously high, triggering a safety shut-off to prevent damage. The most common reason is that water isn't moving through the system quickly enough to carry heat away, often due to a pump failure or a blockage. It can also be caused by a build-up of debris inside the heat exchanger that prevents efficient heat transfer.
DIY fix possible
Check that your home's radiator valves are fully openEnsure your system pressure is between 1 and 1.5 bar on the pressure gaugeTry resetting the boiler by turning the selector switch to 'R' for five seconds
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 E.01 – .20 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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