I found on VAG Simos 18.1 , 18.2 ( I think all Simos 18 ) also problem in Boot mode. I it will communicate with ECU but when it goes to Unlocking , after 1-2 min I get message " ECU rejects to enter session"
The problem is Signal (CFN) wire, On your diagram it has only 1 Signal wire , but it needs to be in 2 places , Everything else is good . After I connect signal wire on those 2 places , it read ECU with out problem.
Here is the picture with correct pin out for Signal wire.
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