2006 Golf 4 speed auto shifting issues

Hello All: This is my first VW. Been working on cars for 50 years. This Golf had all the indications of a failing auto trans valve body. IE, it shifted from 1st to 2nd OK, but would not engage 3rd or 4th. The scan tool I have did not work on VW, so I swapped the valve body out on a hunch. Bolts were torqued to 44 inch pounds, the correct German ATF was used, the new (after market) wire harness was connected and secured, but the same problem exists. Could a speed sensor or TCU be at fault? What is a good scan tool to purchase to diagnose VW issues? Thank you for any tips.