PRAY..it's your only hope :) Merry X-Mas!
Your going to have to help us out Liz ... what light came on? Was it the oil, low coolant, battery , low windshield ... was the light orange or red?
Nice kittykat, the light comes to you during the trip, then what. Short off time, then restart, then does not reset light on? and you are suffering from an attack by the punctuation preponderance poophead? You must get the code reader at the parts store, run tests, see what it leads to , and decide what make, model, and year you are repairing. The crystal ball says , HEGO or 02 code is likely, just a s.w.a.g. You may want to i.d. the powertrain components as well if things get tough. There's google, always always...
There's engine codes.com as well to find your description and definition. They list likely causes for your knuckle busting pleasure. Check gas cap for installed right and tight. Visually inspect parts, and connectors. Know your calibration code for ordering parts. You can update your q, as things progress if you need the skinny on howto.