1999 Plymouth Breeze code reader will not work for my car

I am trying to hook up a code reader to my 99 plymouth breeze and can't get the code reader to respond. The code reader is brand new and was hooked up to 2 other vehicles as a test to find out if the code reader was faulty but it worked fine on both of them. Some history on the car is the check engine light has been on for over a year and a couple months back had problems with the computer and I switched it out with a used one and it runs like a champ again. This car also likes to give trouble with blowing fuses and seeps a large amount oil from the head gasket.
Your expertise will be greatly appreciated!
Thanks