Your boiler is still heating your home, but it can't sense the room temperature properly, so it is relying on the outside weather to decide how warm to make the house, which may make the temperature a little less precise.

DIY fix possible

Check that the wireless room thermostat or room unit has working batteries, and replace them if it is low or flat.Make sure the room unit is not in direct sunlight, near a radiator, or behind a curtain, as these can give false readings.Turn the boiler off at the switch, wait 30 seconds, turn it back on, and see whether the code clears.If the code returns, leave the boiler alone and book a Gas Safe registered engineer to check the room sensor and its wiring.