Either remove fuse F2 in the passenger compartment fuse box or the negative battery cable for 10-15 minutes.
Either will clear the keep-alive memory and will restore all the data tables to defaults.
If your PCM was re-programmed by a tuner or a similar device, that is a different matter.
If your original owner's manual is missing, download a soft copy from www.fleet.ford.com
under the MAINTENANCE tab.
1989 Taurus SHO What a project! Retired at 249K.
1997 Ford F150 SC 5.4L - Gone
1995 Mustang GT Convertible, only 68K miles.
1998 Ford Contour Wifey's old daily driver, now mine.
2001 F250 SD, 6.8L, 4 X4.
2007 Mercury Mariner AWD - Wifey's new daily driver