What is an IPN? How much should it cost to replace? on 2006 Kia Sedona

The Kia wouldn't start one day. We towed it to the shop. First, we were told we didn't put oil in the car, and that is why it didn't start. Then we were told it wasn't the oil, it was the starter. We fixed the starter, and we brought it home. 3 days later we were told it wouldn't start. We brought it back, and now we are being told it is the IPN. What is the IPN and how much should it cost to replace? Also, does it seem to anyone else that the mechanic is just guessing?

Asked by for the 2006 Kia Sedona
Park Neutral switch is the only thing that comes to mind, yes it sounds like a guess to me! These things can be tested, however in the repair persons defense, if problem is intermittent sometimes a guess is all you get!!