Your boiler has stopped working because its internal sensors or control system have detected a technical communication error.

Disconnect the connector of the sensor and press “reset”. When the same fault remains, short-circuiting in the cable loom has occurred or the control panel is defect, otherwise the sensor is defect.

What causes this fault?

This fault occurs when the boiler's brain loses the ability to talk to its internal temperature sensors, usually due to a physical break in the electrical signal. The most common reason is a failed sensor that can no longer send readings, or damaged wiring that has developed a short circuit. If those components are fine, it suggests the main control board has developed a technical defect and can no longer process the information.