I have 09 Suburban. It has factory head unit with DVD, Nav, XM, etc. When I adjust the clock it reverts back to time prior to change when I turn truck off, also it defaults to Nav screen. Sometimes (not always) when getting in car I can hear humming (like when CD ejects) coming from unit before I start truck. Any ideas?

 

Welcome to the forum. The noise you hear is when you open the door, the hard drive for the nav unit starts spinning up so it will be ready to go by the time you get the vehicle started.

 

I appreciate info on Navigation. I guess I just never noticed on my others vehicles. Now if I can fix the clock issue. Thanks for the rapid response.