Do-It-Yourself (DIY) projects:
www.obd-diag.com
1.) for ISO9141-2 and KWP2000; additional VAG.com 311 mode; 9600 or 38400 baud
low-cost-DIY
Manual:
low-cost-scanner
2.) DIY project supporting all OBD2 protocols, additional LAWICEL-mode (can-low-level mode) via
"CAN HACKER", VAG.com 311 mode for VW,Audi,Seat,Skoda. Manual (German):
Bausatz_CNM_4000.pdf
3.) a great hand-held-scanner DIY:
"AGV 4500 expert"
Manual, Eagle .sch .brd data:
Handheld_diskret.zip
finally the AGV4000 data-sheet (in German):
AGV4000-03-2006.pdf