I have a 2000 jeep grand cherokee and the code evap emissions control leak po442 is coming up when I plug the machine in for the check engine light. What does that mean?

Here's a link to a description of the Chrysler EVAP system. The problem can be as simple as a cracked hose, or as bad as a new leak detection pump.

Chrysler EVAP Codes (http://www.ricksfreeautorepairadvice.com/diagnostics/diagnostic-tips/chrysler-evap-testing%E2%80%94how-it-works)