If the” trac off “light comes on, when you are driving the car there is an easy way to reset it.  However, you did not mention what type of car you have, and each type of car has its own set of instructions for this process.  The best way to proceed would be to look in the cars manual.  This is the easiest way to find the correct directions for your vehicle.   If you do not have a manual, you can call the dealership that sells your type of car, ask for the service department, and find out the process from them.  On line at EBAY MOTORS you can buy a manual for most cars for very little money, if you don’t have one, but would to be able to have the information you need, on hand.  Service Departments often sell these manuals too, but they will cost more at the Service Department then it does on line.