03 suburban engine light flashing

my engine light stay on and flashes if i go over 30mph and the car will not go over 50mph.cheched the oil and other fluids.engine seems to rev up smoothly while in park.this is my wife's car.she just left on a 120 mile trip but had to return.anyone know what the problem could be.thanks mr223

Welcome to AF, wrong forum I am moving this to the Suburban forum below.