The reason your light is on is because you need to clean out your EGR System, to remove all the carbon and clean off EGR Temperature Sensor as well if equipped. Then you need to re-set the light that comes on because of mileage. go here to read about the EGR Light re-set procedure, you will have to pay a few bucks, but it is really worth it. There a zillion ways to re-set the EGR lights on various cars, even on Toyota, so the best thing to do is to get real instructions on how to do it. All the best and let me know if you need more help, Merry Xmas!
http://bit.ly/alldata_repair_manuals