2005 Dodge Caravan ckeck engine light

My grand caravan engine light came on recently, and the dealer advised me that everything was working fine, they reset the code told me to drive about 50 miles and the light should turn off, it did as they said but a month ago it came back on again what can I do to get results because the dealership don't want to honor the service warranty we have, is there a way I can find out what is going on within my van and fix the problem my self