My 96 bronco check engine light turn on out of nowhere but with no further complications.. what can it be?

well i was driving to walmart, and I got there and stop, when to do my shoppings and all was fine. I came back and start the vehicle and the check engine light turn on. Is sunday night so all "check engines" places are close. The car drove back home fine with no problems at all. Got home disconnect the battery and connect it back and the light is still there but everything seems fine.. Please help me because since I cant take it to check it out is killing me.... please help