Why do Trac off light and engine light came on at same time when I turn on the car?

This is usually indicative of a problem with the car's emissions control system. The most likely cause is a failure of the catalytic converter, but it could also be due to a problem with the oxygen sensor or other components of the system. In any case, it's best to have the car checked by a mechanic to diagnose the problem and determine the best course of action.