I can not get my S5 to read text messages in the car. Car mode is not in the drop down menu or anywhere in settings that I can find.
Pull down the notification shade, then tap the menu button (the four squares in the upper right-hand corner). Car Mode should be listed toward the bottom.
You should download an app for it. Google Play has some really good ones!
There is no need for an extra app as it's on this phone right in the spot where tikibar1 said and works great. Also you can google to find a lot of stuff on this phone and youtube videos on how to use the various settings on this phone. Mary