GPS example on GrovePi

Hello,

i am a new user of raspberry GrovePi, and i try to use a GPS!
My problem is that my example didn’t work :’( !
i tryed to use the example for GrovePi here seeedstudio.com/wiki/Grove_-_GPS

it return “Unable to read” and the error is in the vals method , lat_ns=GPS.GGA[2] is out of rang.

someone can help me please :’( !?