97 f150 check engine light below quarter tank

i searched all over the board and couldn't find a thread about this problem. it's happened three times now and it's got me confused. when i get between a quarter and an eighth of a tank of gas (before the low fuel light comes on), the check engine light comes on and stays on. i will go off after i fuel up and drive it for a couple of days. when it happens, there is no change in performance or drivability. the last time it happened i had the codes downloaded and the only one i can remember is the 0401 code. it is the 4.2 liter, automatic, regular cab, two wheel drive. plugs, wires, and oil changed within the last 1500 miles. ideas?

Focus on the DTC P0401 ''Insufficent flow EGR''
It sounds like the EGR valve + passages need cleaning, See similar threads.