It appears during the recent repair of your 2000 Ford Taurus Check Engine Light its OBD II computer system was reset; erasing all the emission monitors (readiness flags) from the OBD II computer.
Setting the emission monitors requires driving your Ford Taurus at least 100 miles; consisting of everyday normal driving, stop and starts (like at red lights and traffic), ignition on and off several times a day with at least 15 minute delays in-between (this allows the EVAP monitor to run), and freeway driving at least on three occasions for at least 5 minutes each at speeds above 40 mph.
