Your boiler is still heating your home, but it has lost its wireless signal from the outdoor temperature sensor, so it is guessing the weather and may run hotter or cooler than necessary.

DIY fix possible

Locate the wireless outdoor temperature sensor, usually mounted on an outside wall, often facing north or shaded.Check the sensor's batteries and replace them with new ones if they are low or flat.Make sure nothing is blocking the sensor or its line of sight to the boiler, and that it is not mounted near a large metal object or a new Wi-Fi or radio device.Switch the boiler off at its power supply for about a minute, then switch it back on and check whether the code clears.If the code returns, contact a Gas Safe registered engineer to check the wireless receiver and sensor pairing.