There are many cheap universal OBD-II scanners for about $50. They will work on any '96 or newer vehicle, but they frequently can come up lacking because most vehicle manufacturers have much more than OBD-II functions that can turn on a check light (ABS, Airbag, TCM, Body Control, Radio, Theft, and numerous engine codes and important data that don't show up as an OBD-II code). If you have a laptop PC (it's doable on a desktop with a long USB or serial extension) the best VW scanner is the Ross-Tech VAG-COM software. Note it is VW specific, actually a clone of the actual VW scanner software, not just OBD-II. As with all scanners you will need information to understand what it is telling you. Bentley has both a hadcopy (better for do-it-yourselfers) and factory CD-ROM maunals that can't be beat.
http://www.ross-tech.com/index.html
http://www.bentleypublishers.com/res...htm?subject=20