I have been battling some DTC's, the details of which are in this post: http://www.gmtruckclub.com/forum/showthread.php?51341-EVAP-Purge-Valve-Issue I was wondering if it could possibly be helpful to clear the codes using my programmer then see if they come back. I wasn't sure if that's how it worked or not. I didn't know if maybe you clear a code, it won't come back even if it is still an issue. It's probably a stupid question, but I wanted to make sure before I tried it. Thanks for any help!