As you may already know, on many late model cars if an individual module (ECM, TCM, etc.) is not “talking”, it will not and cannot report any issues. It simply doesn’t communicate. This is particularly common on European cars, BMW for example. With many scan tools, after running a preliminary scan of the vehicle, a technician can find a “communicating modules” section. Alternatively, by reading the quick scan results, the tech can determine that he or she doesn’t see all the modules necessary to operate the vehicle correctly.