What is the process for beginning a class action law suite against a large corp. such as SAAB

We have a 2006 SAAB 93 that was purchased used from a GM dealership. The car is still under warranty and has been in the shop on 6 occasions for the same computer malfunction, that SAAB admittingly confesses they can not fix. These cars are listed on several web sites detailing the same problems and repair scenerios that after the warranty has exspired GM ( SAAB) and its dealership repair shops suddenly find the problem and repair it at a cost of sometimes of several thousand dollars this is to convenant to be believable what should I do to proceed and make SAAB accountable?