V-checker encounter "comm.error" on 2005 Audi A4 Quattro

I bought a V-checker from www., it encounter "comm.error"
1 - Control Module Selection Screen OK
2 - Engine Electronics Selection Screen OK
3 - Can Bus Mode Selection Screen OK
4 - Can Bus Mode Communicate Screen OK
5 - Comm. error!

anyone can help me?

Asked by for the 2005 Audi A4 Quattro
if you have purchased a generic obd scan tool you will only be able to access engine emisions data that is standardised for all vehicles,for any audi specific data you eill need an audi specific scan tool,comm errors can be caused by poor connections,voltage problems or scaners that are not compatible with the obd system you are trying to access,this is more complex than the internet makes it sound,you do not siply plug in the scaner and it tells the tech what to replace,talk to a qualifyed tech for some insight