Not sure what this 'eval line' thing is they're talking about.
You can get your computer codes scanned for free at AutoZone and some other auto parts places. (Unless you live in CA, where they aren't allowed to scan/reset computers)
Ask for the actual code number and post it here and we'll be happy to help you identify the problem. Codes are described here:
http://www.contour.org/FAQ/FAQ.cgi?s=probs&display=checkengine 
