now that this post has clarified a CEL=MIL I will help.

Did you by any chance check the DPFE sensor?
(Gas pressure differential sensor.)
I know Ford re-engineered it and that was my problem.
I was getting ERG 401 and O2 codes as well.

1996 2.5LT V6 Contour ATX My Tour+help/info pics E0 rims, Gutted Pre-Cats,CTA Custom Exhaust & Intake, Diablo Chip.