The light may or may not be related to emissions.  You need to find
out what the code is that turned the check engine light on.  All you
really need is a wire:

   http://www.therangerstation.com/tech_library/OBD_I.html
   http://www.therangerstation.com/tech_library/diagrams/4hup96.gif

After counting the flashes to obtain the code, use these charts to
determine the meaning:
   
   http://www.therangerstation.com/tech_library/2digitcodes.html
   http://www.therangerstation.com/tech_library/3digitcodes.html

Without that information all anyone can do is guess.

HTH,
-D