There is a wonderful tool out there for diagnosing problems and reprogramming options in your Volkswagen. It’s called VAG-COM or VCDS, made by Ross-Tech. It comes in two parts – the adapter that connects to your vehicle, and the software application you run on your PC. The VCDS adapter plugs in to the diagnostic port typically found above the driver’s footwell area and connects to your computer’s USB port. Run the VCDS program and you can access the VW-specific codes that are more detailed than the typical OBD-II codes. You can also change settings such as headlight voltage, rain-sensing wiper function, fuel tank indicator, door locking/unlocking protocol, etc. There are other settings that can be performed to ensure “readiness” after you’ve disconnected your battery or changed out an engine sensor. “Readiness” is VW’s way of saying your car’s fine adjustments are complete and the car is ready to operate. Most readiness elements can be achieved by just driving the car for a day but some items, such as throttle body adjustment, just never seem right unless you perform the readiness checks using VCDS.
It’s pricy to start but pays for itself quickly if you perform your own VW service. Here’s a link to the Ross-Tech website and an example of the interface I purchased several years back that still works flawlessly: http://store.ross-tech.com/shop/VCHUC.html.