Just purchased the parts from Marvin, a canister and valve for a little over $200. I decided to crawl under it yesterday and do the replacement and the check engine light goes off! This truck is playing with me. It did get warmer and I wonder whether temp may play a part in this saga. So, my plan is to drive around with the parts in the back seat cause I know the moment I put them in the garage the check engine light will come back on.