engine systems default light on ?

best thing to do is take it to a dealer and have a scan done,not sure what you mean by default light,the JAG is a complated car to work on,maybe if you can give a little more info,If I had to guess at this,I would say that their is a default malfunction mode in your car that has set it in default mode in the computer to keep it from any real damage.onley a scan will tell what is wrong.

Sounds like your car has gone into Limp Home mode. May be something Engine related and the car is trying to prevent major problems and to get you to safety. Don't gamble in this state. Diagnostic definitely needed.