Your boiler has detected an issue with a temperature sensor normally used in more complex heating systems, often meaning a sensor is faulty or incorrectly configured.

Temperature at hydraulic point: This service function will only be available, if service function 2-A1 is activated.

What causes this fault?

This fault occurs when the boiler's control system loses communication with a specific temperature sensor used to monitor water flow in larger or multi-zone systems. The most common reason is a physical failure of the sensor's internal components or a loose connection in the wiring harness that links the sensor to the main circuit board.