So yesterday I changed my ambient temperature sensor due to the old one being faulty. Now I had a lucky guess to its location as when I searched the net all I could find was people guessing it's location saying it's in the front wing, in the mirror under the windscreen, in the engine bay, where the wiper motors are or they just didn't know which I rather they all said because they was all wrong.
The sensor is in fact behind the lower front grill and to get to it you need to remove the front bumper. This isn't so much a hard task just a fiddly one as getting behind the arches can be a struggle and so can lining it all back up agen after. I'm not sure but you may be able to get to it by removing the right kidney grill, moving the rubber air trap and reaching down to the sensor.
First you need to remove the front bumper there are lots of threads and videos on how to do this but I'll still do a brief description. first you need to remove the headlight washers, I got someone to spray them and before they went back in I grabbed them, there is a little clip where you can use a flat head to remove the bumper panel. There are 4 bolts under the bonnet above the kidney grills undo them next remove the body screws from the front bumper underneath the car and around the inner wheel archs. You will then need to prize the inner wheel arches out with a flat head screw driver ( watch your paintwork ) there will be 2 8mm bolts holding the wing to the bumper. Once all these are undone the bumper should slide off and all you will need to do is remove the 2 fog bulbs.
So the bumper is off and now you can get to the ambient temperature sensor. It can be seen on the right hand side of the bottom grill. To remove it just push it up and it will unclip. To get to it you will need to move the rubber air trap where the kidney grills are and reach down and pick it up. Then all you need to do is unplug it, plug in the new one, push it back in the hole until it clips and then put it all back together agen. Job done.