What do you mean VCDS will fill the gaps? I have the same problem. I scanned with ross-tech cable and found fault code:
02039 - Position Sensor in Transfer Case (G398)
008 - Implausible Signal - Intermittent
02039 - Shareware Version. To Decode all DTCs
008 - Please Register/Activate - Intermittent
Fault code is not listed on ross-tech's page. Have you seen this before?