Your boiler's internal water pressure sensor is not communicating properly with the control board, preventing the system from operating safely.

Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing

What causes this fault?

This fault occurs when the boiler's brain loses contact with the sensor that monitors water pressure, often due to a loose wire or a physical failure inside the sensor itself. Without this vital data, the boiler shuts down as a safety precaution because it cannot confirm there is enough water to operate without overheating.