Resetting Long Term Fuel Trims
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
Long term fuel trim corrections can be reset by resetting PCM Keep Alive Memory (KAM). See KEEP ALIVE RANDOM ACCESS MEMORY RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. After making a fuel system repair, KAM must be reset. For example, if dirty/plugged injectors cause engine to run lean and generate rich long term corrections, replacing injectors and not resetting KAM will now make engine run very rich. The rich correction will eventually be "Learned Out" during closed loop operation, but vehicle may have poor driveability and have high CO emissions while it is learning.