What is wrong with my car? '02 Kia Sedona P0715 code?

We have a KIA Sedona our 2nd. It's a 2005 and we are already having probs. Our first was a 2002. We had probs out of the alternator we had 3 put in it and still had troubles. And I believe the transmission may be whats wrong with yours. It may not be a bad idea if you get new car to drive for the safety of your family. Sorry I couldn't be more help.....