thanks for all the info, guys ( or gals). i did end up changing the EGR valve and the sensor, and the light still came back on. i will try the suggestions in order of simplicity, and see what happens. i still only have 33K miles on the truck. seems to run fine. so i don't know if whatever is causing the light to be on, is hurting anything or not. does anyone know if it might be bad to drive while the light is on?
thanks again for taking time everyone...