High Lockout
P21 on Ideal HP290

Your boiler has stopped working because it cannot accurately tell if there is enough water pressure in the system to operate safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Low Pressure Sensor Error

What causes this fault?

This fault occurs when the boiler's internal computer loses communication with the sensor that monitors water levels. The most common reason is an electrical failure within the sensor itself or a loose connection in the wiring, meaning the boiler shuts down as a safety precaution because it cannot verify if it is safe to fire up.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F1View →P1View →

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