To perform a "calculation" or unlock, the diagnostic tool and the vehicle must undergo a "challenge-response" procedure: What is SFD? - Carista
Understanding VAG SFD Protection: Unlocking Diagnostic Access for 2020+ Vehicles free full vag sfd calculation mhh auto page 1
SFD was introduced to prevent unauthorized tampering and to maintain a record of who makes modifications to a vehicle. To perform a "calculation" or unlock, the diagnostic