P0442 Code on 2017 TRD Sport DCSB

I have a 2017 trd sport dcsb and the check engine light and trac off light came on the other day. I read the code and it came up as P0442 small evap leak. So naturally I cleared the code and made sure the gas cap was on tight. A week later the same thing happens. Since then I tried to turn on the cruise control and that doesn't seem to be working either. I took it down to the dealer, they won't offer any help unless I pay $140 diagnostic fee. Any idea on what this could be? I've seen something from the gen 2's about a secondary air pump, but I haven't found enough info to know if this is true.