Support is away for a few more days. I am wondering what happens when you choose the correct engine? The engine code/size should be stamped on the vehicle ID plate. Alternatively you might be able to look up what engine you car has by finding the manufacture make model year and trim. I can only assume that the Chev system works based on the engine type as a stack of models may be produced with the same engine, for example some Australian cars were produced using Chev LS series V8 motors.