97 Camaro engine codes???

:nono: My son bought a 97 Camaro off a used car lot recently, and now he has the "service engine soon" light on. It runs too rich and is a bit sluggish as well, so he took it to two auto part stores in the area and they both said there was no signal at all. They told him that some underhanded dealers "disconnect" the code source. Has anyone heard of this? How do I re-connect it if this is true?