I have a 2001 Hyundai Sante Fe and the ABS and the TCS light come on in the dash This is after I have been driving for a bit. Sometimes it stays on and sometimes it doesn't.What could be the problem?

Could be the brake system, but most likely the front tone wheels. Replace both while you are at it = they are prone to failure, and Hyundai will not warrant it beyond 5 years despite it being a common problem.