A loose fuel cap or break in the evaporative vacuum lines or fitting can throw a code like this. It is an emission component so likely covered for the original owner, don't know about used. Most states require dealers to warranty used vehicles against emission device failures for like 30 days or so, anything that would cause a failed state inspection.
What code number did they read? Did Autozone reset the code and did it come back?
Most, but not all, of these are loose gas caps. What year did they go to the no gas cap thing?
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac