Hello, I hope the following is of assistance.
This will be due to the ambient air temperature sensor either becoming dislodged or more commonly failing. The sensor is easy enough to replace it is just behind the front panel/cross member, it has 2 wires to it, 1 white/black wire and 1 brown/yellow wire and is labelled as B73 in the diagram below, this diagram is looking from the engine bay towards the front of the car (see the small car picture at the bottom).
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It is usually just clips into place and can come off but normally it's the sensor that fails.
I hope this helps you.