VAG-COM doesn't work on GM to read generic P-codes as a reader. It works on a lot of non-VW/Audi vehicles, none GM. They use an SAE version of the OBD-2 spec, whereas most of the world uses the ISO protocols. (or something like that... this is off of memory). Anyhow, it works with most newer Chrysler products and most European products. Just not Ford and GM. Mark