I bought a beautiful 2002 forest green A4 3.0 Quattro a few months ago that is running perfectly, but the check engine light came on a few days ago.

I got a ProScan OBDII scan tool this January, and after many attempts I can't get it to see my 2002 Audi A4 Quattro. I also could not connect to my 1999 A4 I sold a few months ago. I also tried VCDSLite on my current A4 using the same interface cable, but no joy.

I'm using a USB-to-serial - OBDII adapter that came with ProScan. The driver installed with no errors, and the COM port is initializing, but in 20 tries or so I've never gotten anything but an 'interface not connected' error, from both programs.

I know enough to have installed/configured everything as far as my 16 years in computers will allow (driver, software etc) and I have screwed with the hardware settings until I'm blue in the face. Does anyone have any idea what could be going wrong?

Thanks,
sf