1996 Suburban Code P0441

P0441 "Evaporative Emission System No Flow During Purge". I have searched the forums but couldn't find any on a suburban. 1996 350 Vortec. I first received this code when I put about half a can of Sea-Foam in my gas tank, and then I cleared it and it stayed gone. A month later I put about half a can of Sea-Foam in my gas tank, the code came and then I cleared it and it stayed gone. Now, a few weeks later, I haven't put anything other than gas in my tank and the code popped up a couple days ago and I cleared it, only for it to return today, for which I cleared it again. I've made sure my gas cap is tightened. Should I check all the EVAP lines and tubes? Or should I look into the purge valve? The vehicle runs great and I havent noticed my gas mileage decline so I'm kinda stumped. Any help is appreciated! Thanks!

You would have to power the purge valve either manually with jumper harnesses or a scanner and confirm it operates. Clearing it is not the answer as you can see, the evap system can be troublesome to diagnose without either a smoke machine and a bi-directional scanner.this link may help. http://service.gm.com/gmspo/mode6/pdf/1996/96t57R_HD_yE.pdf