1999 4.0 with code P0455

Hey all !

First I wanted to thank this forum for everyone's help in my previous troubles. You guys /girls are life savers !

My engine light came on a few days ago. I used a code reader which gave me the code P0455 which I know means "EVAP Leak Monitor Large Leak Detected "..
I dont know the first place to look..

I did have code 442 " small leak detected" about a month ago. I just changed the battery last week and now only code 455 came up..

Any Ideas what could be causing code 455 to pop up?

Thanks.

One link:
http://www.obd-codes.com/trouble_cod...cted-large.php

A code p0455 most likely means one or more of the following has happened:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
Other leak or damaged piece in EVAP system

Try the cap first (get a locking one for 15 bucks).