I have an 07 Hyundai Accent. Occasionally when I start it, it will bang into gear and will not shift into high gear. It is an automatic transmission. If I turn it off and restart a couple of times the problem will disappear. I occasionally get the check engine light with this problem but it goes out the same day. It has also occasionally been going down the highway and will shift out of OD and increase rpms. I can pull over and restart and the problem goes away. Any ideas?
Have you checked the level/color condition of the transmission fluid? If not do that first. If the fluid appears fine, then you need to take it to someone with a scanner that can check for history codes. They’ll be able to determine what code was set when the transmission malfuntioned and the Check Engine light came on.
Will the codes show even though the light went out?