My check engine light comes on when I fill up my tank with gas. It goes off when I get below half a tank of gas. I took it to an auto parts store and they checked the code which comes back with a P3400 Cylinder deactivation system bank 1 code. Any Ideas what could be the problem(s)
Strange… fuel level tied into cylinder deactivation circuit somehow… 
??
Silly question (you have the wherewithal to get codes read), but I have to ask, sorry…
(and we need to get this discussion going)
…You have the specified engine oil AND you have checked/rechecked the oil level for proper fill?
CSA