Is the light red or orange? If it's red don't drive it, Have it towed to get it serviced. I had a 2002 4.6 and mine came on at 40K, it was orange. Mine had to do with the a part that failed for the emissions. I did get a letter from Ford sometime before it failing that said they were extending the warranty on that part for an addtional 1 year or 12K miles. Funny why they didn't just recall it and replace it before it failed
I guess they didn't want to if they didn't have to.
Do you have a AutoZone near you? They can scan your OBII port and give you the codes to help see what's wrong.