BoilerFaultCodesYour boiler is having trouble setting up its gas and air mixture correctly, which prevents it from firing up safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Calibration error / calibration procedure not completed
What causes this fault?
This fault occurs when the boiler's internal computer is unable to verify that the gas and air are mixing in the correct proportions for a safe flame. It is usually triggered because the sensors aren't detecting a consistent signal during the start-up phase or the gas valve isn't responding correctly to the calibration commands. This prevents the boiler from firing up to ensure no unburnt gas or dangerous fumes are produced.
DIY fix possible
Check that your gas supply is turned on and other gas appliances are workingPress and hold the 'Reset' button for 5 seconds to clear the faultAllow the boiler to attempt its automatic calibration sequence for several minutes
Find a Gas Safe engineer
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A boiler cover plan would cover faults like F56 — 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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