Your boiler has stopped working because its internal computer is receiving conflicting or faulty information from its temperature sensors.

Sensor or electronics fault | Check NTC's/connections or electronics defect

What causes this fault?

This fault occurs when the boiler's main control board detects a logic error between the heat sensors on the flow and return pipes. It usually happens because one sensor is sending a reading that is physically impossible or because the electrical signals are being interrupted by a faulty circuit board.