There may ba a vacuum hose that was disconnected or is leaking. It also might be caused if the EGR valve is clogged or disconnected. It also could be caused by a bad or disconnected exhaust oxygen sensor. If it is not any of those things, I would either try replacing the spark plugs, or take it to an Auto Zone store; so they can do a free scan to identify the trouble code that is triggering the light. That code will only stay in the computer's memory if the battery is not disconnected before the scan is done.
I hope this helps!!!