Specification :

What is CAN and why is it important?
CAN stands for Controller Area Network. CAN is a new means of communicating with the car for diagnostics used by the latest generations of VW, Audi, SEAT, and Skoda vehicles. Unlike the older ISO9141 system, which used a single K-line for diagnostic communications, the new CAN-Bus system uses a twisted pair of wires with differential signaling. CAN is considerably faster than ISO-9141 ( 500 kpbs vs. 10.4 kbps) . Both new hardware and new software are required in order to communicate with cars using CAN for diagnostics.

What Cars Use CAN for Diagnostics?
All Golf-5 platform cars ( A5 platform)
2003+ VW Touran ( 1T chassis)
2004+ VW Golf ( 1K chassis)
2004+ VW Caddy ( 2K chassis)
2004+ Audi A3 ( 8P chassis)
2004+ Seat Altea ( 5P chassis)
2004+ Skoda Octavia ( 1Z chassis)
2005+ Seat Toledo ( 5P chassis)
2005+ Golf Plus ( 5M chassis)
2005+ Seat Leon ( 1P chassis)
2005.5+ Jetta ( 1K chassis)
2003+ Audi A8 and A8L ( D3 platform, 4E chassis)
2005+ Audi A6 ( C6 platform, 4F chassis)
2005+ Audi A4 ( " B7" platform) ( some control modules)
2005.5+ VW Passat ( B6 Platform, 3C chassis)