I found the same to be true when I tried out that site. I had the VIN of two C-7s to plug in (built several months apart) so I could see what the difference would be. There were differences, but it was difficult to really grasp what was what. As was posted, your dealer will be able to sort it all out.My VIN is 10566 built just before BG shutdown for the Holidays. Going into the website "https://tis2web.service.gm.com/tis2web" as suggested above I'm not sure I understand what I'm seeing for my VIN. It has about 23 different modules and probably submodules listed. On the first page that comes up, there is no mention of any updates required.....maybe that's good. When for example I select the Engine Control Module, it brings up Part numbers and descriptions that look like updates; but I can't tell if they have already been applied or are needed. Almost every module listed has some Part/Description listed.
Can anyone explain how I should be looking at this information and if I can tell if an update is needed......at least without going to a dealer first?