Today on 2018 Ram 1500 My check Engine Light came on followed a few minutes later with a alert on my dash of a loose gas cap. When I pulled over I did notice my gas cap was loose so I re-tightened it.

When I got home the error was cleared on the dash info section but the check engine light renamed on. I hooked up a code reader and obviously received the error P00456 which from my experience with my daughter's car could mean anything from a leak in the evap, a canister or something as simple as a faulty gas cap. Since I had a loose gas cap and that error I just assumed the lesser of the problems so i went to reset the code and I got a "Code reset failure" from my reader. Never saw that before.

Any idea what i can do next? Dont really wanna go an buy a new gas cap because I am sure the problem stemmed from the gas cap being almost off today on its own but I cannot figure out how to reset the error code to remove my check engine light

 

I had the same issue and found out that it takes many driving cycles for the fault to reset itself. It's kind of like the "smog ready" situation where the system needs to see operations at different situations before it will clear the code. Drive it for at least 3 days.