2007 Yaris will not rev

[2007blueyaris]

My girlfriend left her lights on today while she went into work. When she left she had to get the car jumped. The person jumping the car had the cables reversed. The car will now start on its own but will only idle. I can put it in reverse and move, then put it in drive and move but it will only go at idle speed. After a little research I have read that I should disconnect the batter cables for a little bit, try to reset the idle, or check the fuses. Does anyone else have any suggestions? I am in the Chicago suburbs and it is below zero so I am not sure if that has anything to do with it.