My car suddently stoped accelerating

I have an 05 nissan maxima the check engine light
is always on but my car ran fine but today as i was
driving it sudently just started to decelerate and
iwould push the accelerator as far asit goes and it
would not accelerate it wpuld jiat go at a speed of
2.as if it were in neutral and the bateery light was
on??.but i turned it off and on and tried to acelerate
again and nothing just super slow anibody can
tellme whats wrong???