I bought a OBDII when I got my A8 in 2004 to work with all audis up to 2003. This is the serial version and not USB. The only problem is not many new laptop has serial port any more except some Dell models or IBM. Anyhow, the software is free from Rosstech website . We can’t do a lot with this free version, but for reseting and setting some options, it’s extremely handy. We use an old-old laptop from Dell which has a serial port with windows2000.
The serial OBDII online for about $35 back then that works wonder.
Where to hook it up to in A8
Check Engine Light & Airbag are on
Hook up to serial port on laptop, TURN ON THE IGNITION TO AC with all lights are ON.
Execute the VAG-COM Release 311-2.exe file, we will have some port configuration problems.
Select engine for “Check Engine Light” and it shows Fault Codes – 02
Click Fault Codes -02 to see codes and click clear codes -05 to clear the codes.
Now go back to select control module to select airbag to clear airbag codes and follow the same procedure.
Clear codes and check start the engine to see if all lights are gone.
Please read the Ross-Tech instruction carefully and choose the OBDII correctly, because this one really access the car CPU module which can be corrupted with wrong code writing and the car becomes dead. Well, that’s what they say, try with your own risks as always.