check engine light

My 1997 F-150's check engine light came on as soon as it flipped 67000. The handy little owners book says, it's an emissions control problem. Can anybody help ? My truck runs perfect. :banghead:

post a message with the diagnostic trouble code
for it could be one of about 200 different codes withthat many reasons for the light to come on it is hard to give out any info as to what sys to check and how to check it