I'm trying to help a friend with a 2004 Saturn Vue 3.5 engine. Code P0446 won't go away. I found a stuck purge valve and replaced it, still kept setting the code. The gas cap was in sad shape and wouldn't seal properly, replaced it. Still setting the code. I'm now planning on checking the charcoal canister andd valve, but it seems I've always found that to set a different code (P0449). Does anyone know where I should be looking next?