P219A Code, no check engine light

[peglegdev]

So the P219A code came up from a random engine code check due to mpg loss, I don’t have a check engine light, but recently I’ve lost about 6mpg having to fill up at 250-260 miles, same fuel 93 octane same gas station, I’ve read a couple of forums saying it could be a couple of things but none of them state fuel mpg loss I don’t wanna start replacing parts I don’t need to. If anyone could point me in a direction or if someone who has ran into this issue help me out, please and thank you.