This is how to repair the cheap China FVDI if it connects to pc and starts software but says no connection to car when you try to read anything.
Checked obd by measuring connection fra serial to obd as it can’t be opened. All pins came out positive in obd.
Post the PCB…Here comes pics
Tried Vag, BMW
After resolder it could only read bsi on a Peugeot 307 from 2001.
It was can as i use can with pp2000.
First check the cables and the soldering of usb plug on the board mine did lose and had same problem chinese do solder it with eating sticks
Solved! First see F1 (small fuse), try restore point.
Resoldered a few points and it worked
Note that FVDI now has been stopped production. And FVDI2 comes with hardware improvement. Look here: http://www.obd2diy.fr/wholesale/fvdi-abrites-commander-avec-tous-16-logiciels.html