Sure you can trade your car for a new car. However...........do you still have a loan on the old car? How much do you still owe? How much is your old car actually worth as a trade (check www.kbb.com
If you still owe more than your car is worth, you are "upside down" which means you have nothing to trade. If the difference is small, dealers can sometimes juggle the numbers such that the difference is rolled over into a new loan. But if the difference amount is large, they can't. Unless you can come up with cash for the difference, you won't be able to trade.
If your old car is paid off, or nearly paid off, or if you owe less than the car is worth, then you should have no problems.