Car preferences function working in Change preferences menu?

[LacViet]

I just got the 920T and it works great so far; however, the icon Car preferences in the Change preferences menu is always in grey color which obviously I can not change the preference either "link night view to headlights" or "instructions mute car radio" which is said in the Tom tom instruction handbook (in pdf file). Is this function works on everyone 920?

 

[just4fn]

mine is grayed also.

 

[Richard22b]

Built in units

I believe this option is for built in units. The software caters for all versions of TomTom so of course some have options that are not available on others.