With a scan tool. There are lots of scan tools on the market. The VW specific tool that many people on here use is the Ross Tech one (I have one) that you use with a laptop. There are other non-VW specific tools out there that even run on Palm or PocketPC devices. I ordered an Auterra unit to try out with my Palm IIIc.
The OBD connector is behind a panel above your cigarette lighter (on a Mk3). Remove the ashtray and slide the panel to the left expose the OBD jack.
A forum community dedicated to all Volkswagen owners and enthusiasts. Come join the discussion about performance, builds, modifications, classifieds, troubleshooting, maintenance, new releases, and more!