will not sync anymore, stopped suddenly
The first thing you can try and do is a reset. Hold the sleep/wake and home buttons together until you see the Apple logo and then release. If that doesn't help, then look at this support document http://support.apple.com/kb/TS1559 for help. You can also try going to Settings, General, Reset, Reset Network Settings.
Connecting to the vehicle is not really syncing, that is what confused me about your original post. See if these things help.