BoilerFaultCodesYour boiler has detected a sensor error that prevents it from firing up, meaning your heating and hot water will not work until it is fixed.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Simultaneous Lighting Sequence - Thermistor
What causes this fault?
This fault occurs when the boiler's internal thermometer, known as a thermistor, fails to provide a consistent temperature reading to the main control board. The most common reason is that the sensor has developed an electrical fault or has become disconnected, meaning the boiler can no longer safely monitor how hot the water is. Because the system cannot verify the water temperature, it shuts down immediately as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like LED 1 & 2 Simultaneous Fast Flashing (8Hz) — no call-out fees, no surprises.
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