Ford Taurus Forum : “* "Check Engine" light on?”

i would take to a parts store so they can scan it before it does become an issue most of the time the scanning can be free

go to autozone.  they will do a check for free and tell you what you need to fix

Check your fuel cap.... If it is not properly screwed on you will get a check engine light. It may not go off until you drive it a bit then shut it off and next time you run it should be off.. Happened on my wifes 06 taurus and on my 99 old's silhoutte van...

Running on low grade fuel can foul up the O2 sensor, and cause this to happen as well.

Too much Ethanol in a non Flex will do that too.  They'll tolerate 40% w/o a problem.  Over that it thinks it's lean.

Could be a myriad of reasons. Sensors fail, gas caps aren't sealing properly, a small misfire that can go unnoticed... Just head to your local autozone and they'll tell you what the code is and means.