Well, to be exactly sure what it might be, you should diagnose the car. Over by the passenger's side below the glove box and near the heater blower plugs, there should find a little blue plug that plugs into no where. This plug has only two wires. What you could do is create a short. Plug a metal conductor from one hole to the other. Now turn the key to on and see what the check engine light tells you. Since there is something wrong with your car, you should see the check engine light blink. See what code it gives you then look it up on the internet or a manual.