the warning lights have stayed on when starting up 2 different times. The first time they went off after driving car for awhile and then restarting. Called dealer they said probably sensor in rear tire cost $300 is this a possible problem?? Not covered by warranty on my 2014 Santa Fe.

 

Something in your presentation does not add up.
Pretty sure nothing in the rear tire will cause the ABS light to come on.
Don't know what kind of warranty you have, so cannot say..
Stability control relies on info from the ABS (Anti-lock brake system).
Wheel speed sensors are part of the ABS .
There could be a problem present when you first turn the key on OR after you drive the vehicle.
This should be checked with a good quality scan tool to get some guidance..

 

Would get scanner capable of reading the ABS module and scan for codes??