2015 Tundra 4.7 l. About a month ago my engine light came on when I reached 1/2 tank. Filled it up, it would go away. Read in the forum that at one time I may of overfilled it and to just cycle a couple tanks and see what happens. Check engine light continued to come on half a tank, now it’s on all the time. Went to NAPA and got a P0441 code. “Evaporative emission system incorrect purge flow”. Start with the gas cap and work my way through? Any way to self test any parts?