This is for a 03 altima 2.5L i am trying to figure out what it wrong for a relative. Anyways they stated that the car would not go over a certain mph and then shortly after the car would not move at all. After inspection i found that when you press the gas pedal there is no reponse. So i bought a new accelerator pedal sensor and replaced it and still does the same thing. I can press the pedal all the way down and the rpm will only move a little..Is there anything else that would cause this? I also noticed the alternator light was on which im guessing is indicating that the alternator is bad as well. Would a bad alternator cause the pedal not to work or could it be something else? It did have a check engine light on. I pulled the codes and they were p0733 and p0507..before this the car ran perfect, no misfire or anything.

Alternator can cause this forsure. I'd start there. I'd also check the battery could have a dead cell. I just went through this same issue