updated my iPhone 4 when was travelling in China and did not have full capability of Apple Maps (GPS and turn by turn directions etc). Now 'm back in USA upgraded to ios 6.0.1 still can't get maps to show turn by turn directions

I updated my iPhone 4 when I was travelling in China and did not have the full capability of the Apple Maps (GPS and turn by turn directions etc). Now I'm back in USA, upgraded to ios 6.0.1 still can't get the maps to show turn by turn directions. I wonder what I can do. I've tried holding the home and power button for 10 secs and restarting it but no success. Please help.