0300 engine code

Today wife going to work engine light came on she said no power gas pedal did nothing. We bought the car off her mother, sitting awhile 6 months with a full tank. Put 170 miles or so before this incident. Would not start. Had it towed home. Three hours later it started no problem. Scanned it 0300 came up. Question is, can't find problem did notice gas was under a 1/4 tank put fresh gas in it took it for a ride 10 miles or so ran great lots of power no codes. Could bad ethanol gas be the culprit? Thank, s ED