My Outdoor Temperature Gage Always Reads ---F

I just bought a 2001 New Passat and where it is supposed to show the outdoor temperature it says ---F
Thats right, Dashes degrees Fahrenheit...
I just got it and i looked in the manual to see if there is something i need to do to change it or get it to give the temperature but i dont see anything.

What do i need to do to get it to

look through the front middle bumper grille on the bottom, there should be a little sensor on the driver side of the grille , thats the outside temp sensor

look through the front middle bumper grille on the bottom, there should be a little sensor on the driver side of the grille , thats the outside temp sensor

Ok... how much does it cost to replace this