2010 Nissan Sentra 2.0L Code P1778

[cordobe]

While taking my 2010 Sentra on long distance drives on the freeway, the car begins to lose power and the accelerator begins failing to respond and will not go above 60 mph. While going uphill the car starts to lose even more power and even though I'm pressing the gas all the way, it doesn't gain any speed and begins to lose speed. When I got home, I troubleshot with my scanner and it showed the code P1778. I looked it up in the car manual and it reads "Step Motor Function". The car has 85000 miles on it. If anyone has any suggestions on how to fix this issue, or if you have experienced a similar issue, please let me know.