check engine code O 520284

with 31 under it. long story short , I bought this 16 900s eps, about a month ago around 50 miles this code started to come up, at 1st I thought I may of accidently put it in safe mode, this only happens at slow speed when you want to start to get on it their will be "nothing" at the pedal, it will just slow down and shut itself off, then restarts and works fine. the dealer looked at it and said it was fine disconnected the battery and I was on my way. I road it about 150 miles since and it just happened again, anyone have this problem?