GM's cd laser assemblies have a 100 percent failure rate. Remove the radio and take it to the dealer to have them ship it to one of their two grossly over-priced authorized repair centers. They will replace the entire mechanism.
GM stopped allowing us to buy radio service manuals after the '94 model year because they wanted to lock up all that repair business for themselves. Then, to combat owners who were buying less expensive, higher-quality aftermarket replacements, they started building the Body Computers into some 2002 models. These are just a few of General Motor's extremely customer-unfriendly business practices that keeps them profitable.